a is inversely proportional to (b - 4).
If a = 8 and b = 22, express a in terms of b.

Answer:

32.8 miles

Step-by-step explanation:

Amy is driving to Seattle. Suppose that the remaining distance to drive (in miles) is a linear function of her driving time (in minutes). When graphed, the function gives a line with a slope of -0.95. See the figure below. Amy has 48 miles remaining after 31 minutes of driving. How many miles will be remaining after 47 minutes of driving?

Answer: The general equation of a line is given as y = mx + c, where m is the slope of the line and c is the intercept on the y axis. Given that the slope is -0.95, substituting in the general equation :

y = -0.95x + c

Amy has 48 miles remaining after 31 minutes of driving, to find c, we substitute y = 48 and x = 31. Therefore:

48 = -0.95(31) + c

c = 48 + 0.95(31)

c = 48 + 29.45

c = 77.45

The equation of the line is

y = -0.95x + 77.45

After 47 minutes of driving, the miles remaining can be gotten by substituting x = 47 and finding y.

y = -0.95(47) + 77.45

y = -44.65 + 77.45

y = 32.8 miles

Answer:

A.) x=90°

Step-by-step explanation:

Note:

The triangle shown is an isosceles triangle, which means that it has 2 congruent sides (as shown by the small intersecting lines), and this also means that it has two congruent angles.

We are given an angle measure adjacent to one of the missing angles. These two form supplementary angles, which means that they're sum is equal to 180°, or a straight line. So, to find:

[tex]180=135+y[/tex]

y is the unknown angle. Solve for y:

[tex]180-135=y\\\\y=45[/tex]

y is 45°. Since this and the other angle are congruent, add:

[tex]45+45=90[/tex]

Note:

Triangles angles will always add up to a total of 180°.

To find the missing angle x°, use:

[tex]180=a+b+c[/tex]

These are the angles in a triangle. Substitute any known values and solve:

[tex]180=45+45+x\\\\180=90+x\\\\180-90=x\\\\x=90[/tex]

The missing angle x° is 90°.

:Done

Answer:

The speed of the airplane in still air is 550 mph.

The speed of the wind is 50 mph.

Step-by-step explanation:

speed = distance / time

distance = speed * time

or simply

d = st

Let v be the speed of the airplane with no wind.

Let w = speed of wind

With the wind:

d = 1800; s = v + w; t = 3

1800 = 3(v + w)

Against the wind:

d = 1800; s = v - w; t = 3.6

1800 = 3.6(v - w)

We have a system of two equations:

3(v + w) = 1800

3.6(v - w) = 1800

Divide both sides of the first equation by 3. Divide both sides of the second equation by 3.6.

v + w = 600

v - w = 500

Add the equations.

2v = 1100

v = 550

The speed of the airplane in still air is 550 mph.

v + w = 600

550 + w = 600

w = 50

The speed of the wind is 50 mph.

Answer with explanation:

Sales    Commission(10% of sales)

$2,200      0.1×$2,200= $220  

$2,000       0.1× $2,000= $200

$3,134      0.1×$3,134=$313.4

$2,417         0.1×$2,417=$241.7                  

$2,579        0.1×$2,579 =$257.9

The completed table is given as follows

Day   Sales    Commission      Non-Sales pay        Earning

                    (10% of sales)                           (Commission +Non Sales pay)

Mon  $2,200      $220             $9.50                $220+ $9.50=$229.50

Tue   $2,000         $200                 $9.50                $200 +$9.50=$209.50

Thurs  $3,134      $313.4               $9.50                $313.4+ $9.50=$322.9  

Fri     $2,417         $241.7               $9.50                $241.7+$9.50= $251.2

Sat    $2,579        $257.9                 $9.50                $257.9+$9.50=$267.4

Answer:

Yes it suggest that the actual percentage of type A donations differs from 40%, the percentage of the population having type A blood.

Well if a significance level of 0.05 is used it will not affect the conclusion

Step-by-step explanation:

From the question we are told that

     The  sample size is   [tex]n = 149[/tex]

     The  number that where  type A blood is  k =  76

       The population proportion is   [tex]p = 0.40[/tex]

       The  significance level is  [tex]\alpha = 0.01[/tex]

Generally the sample proportion is mathematically represented as

      [tex]\r p = \frac{k}{n}[/tex]

=>    [tex]\r p = \frac{76}{149}[/tex]

=>    [tex]\r p = 0.51[/tex]

The  Null hypothesis is   [tex]H_o : p = 0.41[/tex]

The  Alternative hypothesis is  [tex]H_a : p \ne 0.40[/tex]

Next we obtain the critical value of [tex]\alpha[/tex] from the z-table.The value is  

       [tex]Z_{\alpha } = Z_{0.01} = 1.28[/tex]

Generally the test statistics is mathematically evaluated as

           [tex]t = \frac{\r p - p }{ \sqrt{ \frac{p(1-p)}{n} } }[/tex]    

substituting values

           [tex]t = \frac{0.51 - 0.40 }{ \sqrt{ \frac{0.40 (1-0.40 )}{149} } }[/tex]    

           [tex]t =2.74[/tex]

So looking at the values for t  and  [tex]Z_{0.01}[/tex] we see that  [tex]t > Z_{0.01}[/tex] so we reject the null hypothesis. Which means that there is no sufficient evidence to support the claim

Now if [tex]\alpha = 0.05[/tex] , the from the z-table the critical value for [tex]\alpha = 0.05[/tex] is  [tex]Z_{0.05} = 1.645[/tex]

So comparing the value of  t and  [tex]Z_{0.05} = 1.645[/tex]  we see that [tex]t > Z_{0.05}[/tex] hence the conclusion would not be different.

Answer:

Step-by-step explanation:

from the question,

the mean 14

the standard deviation is 3

and sample size is 10.

since the n which is the sample size is 10, then the distribution is mound shaped.

why?

this is due to the fact that the random variable from which we took the sample is mound shaped.

The sampling distribution of the mean is normally distributed although the question says the random variable is not normally distributed. so the shape is bell shaped and normally distributed.

the standard deviation of the mean is

3/√10

= 0.948

Answer:

C. 50 degrees

Step-by-step explanation:

Because 6x + 5x = 110° and x = 10

5×10 = FEG 50°

Answer:

A

  [tex]t = 10.1[/tex]

B

  [tex]p-value = p(t > 10.1)= 0.000[/tex]

C

  [tex]0.4714 < p_1 - p_2 <0.6988[/tex]

D

  The  oxygen treatment  is effective because

1 the is no 0 in the interval telling us that the treatments are different

 2 the upper and the lower limit are positive tell us that the proportion of those treated by the oxygen treatment is greater

Step-by-step explanation:

From the question we are told that

    The  first sample size is  [tex]n_1 = 140[/tex]

     The  number of patient which the oxygen cured is k = 113  

     The second sample size is  [tex]n_2 = 158[/tex]

     The number of patient that  placebo cured is  l =  35

The first sample proportion is

           [tex]\r p_1 = \frac{ 113}{140 }[/tex]

           [tex]\r p_1 = 0.8071[/tex]

The second sample proportion is  

           [tex]\r p_2 = \frac{ 35}{ 158 }[/tex]

          [tex]\r p_2 = 0.222[/tex]

The null hypothesis is  [tex]H_o : p_1 = p_2[/tex]

 The  alternative hypothesis is  [tex]H_a : p_1 > p_2[/tex]

Let assume the level of significance be[tex]\alpha = 0.05[/tex]

Generally the pooled proportion is mathematically evaluated as

    [tex]p = \frac{p1 * n1 + p2 * n2}{n1 + n2}[/tex]

substituting values

     [tex]p = \frac{0.8071 * 140 + 0.222 * 158}{140 + 158}[/tex]

      [tex]p = 0.4969[/tex]

Generally the standard error is mathematically represented

      [tex]SE = \sqrt{ p(1- p ) * [ \frac{1}{n_1} + \frac{1}{n_1}] }[/tex]

      substituting values

     [tex]SE = \sqrt{ 0.4969(1- 0.4969 ) * [ \frac{1}{140} + \frac{1}{158}] }[/tex]

     [tex]SE = 0.0580[/tex]

Generally the test statistics is mathematically represented as

       [tex]t = \frac{ \r p_1 - \r p_2}{ SE}[/tex]

       [tex]t = \frac{ 0.8071 -0.222}{ 0.0580}[/tex]

       [tex]t = 10.1[/tex]

The  p-value is from the normal distribution table as  

      [tex]p-value = p(t > 10.1)= 0.000[/tex]

given that [tex]t< \alpha[/tex] the null hypothesis is rejected

From the normal distribution table the critical value of  [tex]\frac{\alpha }{2}[/tex]  is  

     [tex]Z_{\frac{\alpha }{2} } = 1.96[/tex]

Generally the margin of error is mathematically the represented as

         [tex]E = Z_{\frac{\alpha }{2} } * SE[/tex]      

         [tex]E = 1.96 * 0.0580[/tex]      

          [tex]E = 0.1137[/tex]

The 95% confidence interval is mathematically  represented as

           [tex](\r p_1 - \r p_2) - E < p_1 - p_2 < (\r p_1 - \r p_2) + E[/tex]

substituting value

             [tex](0.8071 - 0.222) - 0.1137 < p_1 - p_2 < (0.8071 - 0.222) + 0.1137[/tex]

             [tex]0.4714 < p_1 - p_2 <0.6988[/tex]

The  oxygen treatment  is effective because

1 the is no 0 in the interval telling us that the treatments are different

 2 the upper and the lower limit are positive tell us that the proportion of those treated by the oxygen treatment is greater

Answer:

Step-by-step explanation:

From the given information;

Angela took a general aptitude test and scored in the 90th percentile for aptitude in accounting.

What percentage of the scores were at or below her score?

The percentage of scores that were at or below her score is

Percentage P = 90%

This benchmark is more than average, so we can typically say more of the scores were at or below her score

What percentage were above?

Since The percentage of scores that were at or below her score is

Percentage P = 90%

Then the percentage of the scores that were above will be : (100 -90)%

= 10 %

We can see here that  less percentage of score were above Angela's Score.

Step-by-step explanation:

Exterior angle BOA = 250°

Interior angle BOA = 360°- 250° = 110°

Now,

(A) BDA = interior angle BOA / 2 = 55°( Property of circles)

(B) From the figure, we observe that AOBC is a cyclic quadrilateral (i.e. sum of opposite angles is 180°).

Therefore, BCA + BOA = 180°

BCA = 180° - 110° = 70°

Answer:

(x=6) is less than 18 which would give you the cost of the current plan

Step-by-step explanation:

If you take six, first you must multiply 4.50 by 6, ($27) then add it, to $94, giving you $121. Now we have to find which phone will give us the same cost, for this I choose 18. if you do 18 x 4.50, you get $81, and if you add this to 94, it gives you 175.

Answer:

Cohen's D

Step-by-step explanation:

Cohen's D is a statistic that measures effect size. It shows standardised difference between 2 means.

Effect size is defined as how large the effect of a something is or its magnitude.

Cohen's D works effectively when the sample is >50 (that is for large samples). However a correction factor can be used to make results from small samples more accurate

The formular for Cohen's D is:

D = (mean1 - mean2) ÷ (√({standard deviation1}^2 + {standard deviation 2}^2)/2)

This is the most appropriate method in the given scenario

Answer:

Null hypothesis: μ = 407

Alternative hypothesis: μ < 407.

Step-by-step explanation:

In this case, the machine is SUPPOSED to fill the bag so that the bag weighs 407 grams. So, the null hypothesis will be that the machine is doing what it is supposed to be doing. And so, μ = 407 grams would be the null.

The worker thinks the machine is filling the bags to LESS THAN what it is supposed to. So, the alternative hypothesis is that the machine is NOT doing what it is supposed to and μ < 407 grams.

Hope this helps!

Answer:

29 years of experience.

Step-by-step explanation:

So let's take the expression step by step.  Remember that you need to follow the order of precedence here for the operations.  Parentheses, exponentials, multiplication, and addition.

-5 + { 4 * 6 + 3 + 1 + [ 3 - ( 4 - 8 ) + ( 3 - 2 ) ] }

-5 + { 4 * 6 + 3 + 1 + [ 3 - ( -4 ) + ( 1 ) ] }

-5 + { 4 * 6 + 3 + 1 + [ 3 + 4 + 1 ] }

-5 + { 4 * 6 + 3 + 1 + [ 8 ] }

-5 + { 24 + 3 + 1 + 8 }

-5 + { 36 }

29

So the teacher has 29 years of experience.

Cheers.

Answer:

D) 1562.4 cubic centimeters

Step-by-step explanation:

volume = area of the base × height

volume = 173.6cm² × 9 cm

volume = 1562.4 cm³

Answer:

[tex]f(x) =3\,*\,\,4^x[/tex]

Step-by-step explanation:

to find the equation of an exponential function, just points on the function's graph  are needed.

Recall that the exponential function has a general expression given by:

[tex]f(x) = a \,e^{b\,x}[/tex]

so we impose the condition for the function going through the first point (0,3) as:

[tex]f(0) = a \,e^{b\,(0)}= 3\\a\,e^0=3\\a\,(1)=3\\a = 3[/tex]

Now,knowing the parameter a, we can find the parameter b using the other point:

[tex]f(1) = 3 \,e^{b\,x}= 12\\3\,e^{b\,(1)}=12\\e^b=12/3\\e^b=4\\b=ln(4)[/tex]

Therefore, the function can be written as:

[tex]f(x) = 3 \,e^{ln(4)\,x}=3\,\,\,4^x[/tex]

Answer:

C)

h(x) = 3(4)x

Answer:

48 soldiers

Step-by-step explanation:

60 soldiers                    20 days

x soldiers                       100 days

60 x 20 = 1200 = 100x

Therefore x = 1200/100 = 12

60 - 12 = 48

Hope that helped!!! k

Answer:

30 Soldiers

Step-by-step explanation:

Given:

1) No of soldiers=60

No of days=20

2) No of days=100

No of soldiers=?

No of soldiers to leave=?

Solution:

Let us use the cross multiplication method.

Let x be the no of soldiers.

No of days                                     No of  soldiers

1) 20                                                     60

2) 100                                                    x

by cross multiplying,

20x=100 x 60

20x=600

x=600/20

x=30 soldiers

Therefore, No of soldiers to leave =60-30=30 soldiers

Answer: I think it is C

Step-by-step explanation:

There is no answer because A can be many solutions, B is x = -25, you just cannot solve C, and D is y = 7/6

Answer:

We conclude that prenatal cocaine exposure is associated with lower scores of four-year-old children on the test of object assembly.

Step-by-step explanation:

We are given that the 190 children born to cocaine users had a mean of 7.3 and a standard deviation of 3.0 The 186 children not exposed to cocaine had a mean score of 8.2 with a standard deviation of 3.0.

Let [tex]\mu_1[/tex] = population mean score for children born to cocaine users.

[tex]\mu_2[/tex] = population mean score for children not exposed to cocaine.

So, Null Hypothesis, : = 490      {means that the prenatal cocaine exposure is not associated with lower scores of four-year-old children on the test of object assembly}

Alternate Hypothesis, : 490     {means that the prenatal cocaine exposure is associated with lower scores of four-year-old children on the test of object assembly}

The test statistics that will be used here is Two-sample t-test statistics because we don't know about population standard deviations;

                               T.S.  =  [tex]\frac{(\bar X_1-\bar X_2)-(\mu_1-\mu_2)}{s_p \times \sqrt{\frac{1}{n_1}+\frac{1}{n_2} } }[/tex]  ~ [tex]t__n_1_+_n_2_-_2[/tex]

where, [tex]\bar X_1[/tex] = sample mean score of children born to cocaine users = 7.3

[tex]\bar X_2[/tex] = sample mean score of children not exposed to cocaine = 8.2

[tex]s_1[/tex] = sample standard deviation for children born to cocaine users = 3

[tex]s_2[/tex] = sample standard deviation for children not exposed to cocaine = 3

[tex]n_1[/tex] = sample of children born to cocaine users = 190

[tex]n_2[/tex] = sample of children not exposed to cocaine = 186

Also, [tex]s_p=\sqrt{\frac{(n_1-1)\times s_1^{2}+(n_2-1)\times s_2^{2} }{n_1+n_2-2} }[/tex]  = [tex]\sqrt{\frac{(190-1)\times 3^{2}+(186-1)\times 3^{2} }{190+186-2} }[/tex] = 3

So, the test statistics =   ~

                                     =  -2.908

The value of t-test statistics is -2.908.

Now, at a 0.05 level of significance, the t table gives a critical value of -1.645 at 374 degrees of freedom for the left-tailed test.

Since the value of our test statistics is less than the critical value of t as -2.908 < -1.645, so we have sufficient evidence to reject our null hypothesis as the test statistics will fall in the rejection region.

Therefore, we conclude that prenatal cocaine exposure is associated with lower scores of four-year-old children on the test of object assembly.

In the null hypothesis, a test always forecasts no effect, while the alternate theory states the research expectation impact, and calculation as follows:

Calculating the pooled estimator of [tex]\sigma^2[/tex], denoted by [tex]S^2_p[/tex], is defined by

[tex]\to \bold{S^2_p= \frac{(n_1 - 1) S^2_1+ (n_2 - 1)S^2_2}{n_1 + n_2 - 2}}[/tex]

Null hypothesis:

[tex]\to H_0 : \mu_1 - \mu_2 = \Delta_0\\[/tex]

Test statistic:

[tex]\to T_0=\frac{\bar{X_1}- \bar{X_2} -\Delta_0}{S_p \sqrt{\frac{1}{n_1}+\frac{1}{n_2}}} \\\\[/tex]

Alternative Hypothesis:

[tex]H_1 : \mu_1 -\mu_2 \neq \Delta_0\\\\ H_1 : \mu_1 -\mu_2 > \Delta_0\\\\H_1 : \mu_1 -\mu_2 < \Delta_0\\\\[/tex]

Rejection Criterion

[tex]t_0 > t_{\frac{\alpha}{2} , n_1+n_2 -2}\ \ \ or\ \ \ t_0 < - t_{\frac{\alpha}{2} , n_1+n_2 -2} \\\\t_o > t_{\alpha , n_1+n_2 -2} \\\\t_o > -t_{\alpha , n_1+n_2 -2}[/tex]

Given value:

[tex]\to S_p=9\\\\\to \Delta_0=0\\\\\to t_0=-\frac{0.9}{3(\sqrt{(\frac{1}{190}+\frac{1}{186})})}=-2.9\\\\\to t_{0.05,374}=1.645\\\\[/tex]

here

[tex]\to t_0 < -t_{0.05,374}[/tex]

hence rejecting the [tex]H_0[/tex]

Since there should be enough evidence that prenatal cocaine exposure is linked to inferior item assembly scores in 4-year-olds.

Find out more about the alternative hypothesis here:

brainly.com/question/18831983

Answer:

[tex] Perimeter = 3x + 3 [/tex]

Step-by-step explanation:

Perimeter of the given triangle in the figure is the sum of all three sides.

The expressions for the 3 sides are given as, [tex] x, (x - 3), (x + 6) [/tex].

Therefore,

[tex] Perimeter = x + (x - 3) + (x + 6) [/tex]

Simplify,

[tex] Perimeter = x + x - 3 + x + 6 [/tex]

Collect like terms

[tex] Perimeter = x + x + x - 3 + 6 [/tex]

[tex] Perimeter = 3x + 3 [/tex]

Answer:

rose. is. 18/2=9 years old

Answer:

Stephanie is 18years old and she is twice older than her sister

so rosa is 18÷2(since stephanie is twice older than rosa

so rosa is 9 years old

Answer:

219.80 feet

Step-by-step explanation:

Tan 20= 80/b

Tan 20= 0.363970234266

(0.363970234266)b=80

b= 219.80 feet

The distance between the sculpture and the bottom of the building is required.

The distance between the building and sculpture is 219.80 feet.

[tex]\theta[/tex] = Angle of depression = Angle of elevation = [tex]20^{\circ}[/tex]

p = Height of building = 80 feet

b = Required length

From the trigonometric ratios we have

[tex]\tan\theta=\dfrac{p}{b}\\\Rightarrow b=\dfrac{p}{\tan\theta}\\\Rightarrow b=\dfrac{80}{\tan 20}\\\Rightarrow b=219.80\ \text{feet}[/tex]

Learn more about trigonometry:

https://brainly.com/question/23899312

Answer:

50.93

Step-by-step explanation:

Add up the frequencies:

2 + 5 + 14 + 15 + 21 + 18 + 15 + 9 + 2 = 101

Divide by 2: 101/2 = 50.5

So the median is the 51st number, with 50 below and 50 above.

Add up the frequencies until you find the interval that contains the 51st number.

2 + 5 + 14 + 15 = 36

2 + 5 + 14 + 15 + 21 = 57

So the median is in the group 49.5 − 51.5.  To estimate the median, we use interpolation.  Find the slope of the line from (36, 49.5) to (57, 51.5).

m = (51.5 − 49.5) / (57 − 36)

m = 2/21

So at x = 51:

2/21 = (y − 49.5) / (51 − 36)

y = 50.93

Answer:

The critical value for two tailed test at alpha=0.1 is ± 1.645

The calculated  z= 9.406

Step-by-step explanation:

Formulate the hypotheses as

H0: p1= p2 there is no difference between the population scrap rates between the old and new cutting methods

Ha : p1≠ p2

Choose the significance level ∝= 0.1

The critical value for two tailed test at alpha=0.1 is ± 1.645

The test statistic is

Z = [tex]\frac{p_1- p_2}\sqrt pq(\frac{1}{n_1} + \frac{1}{n_2})[/tex]

p1= scrap rate of old method = 62/200=0.31

p2= scrap rate of new method = 36/400= 0.09

p = an estimate of the common scrap rate on the assumption that the two rates are same.

p = n1p1+ n2p2/ n1 + n2

p =200 (0.31) + 400 (0.09) / 600

p= 62+ 36/600= 98/600 =0.1633

now q = 1-p= 1- 0.1633= 0.8367

Thus

z= 0.31- 0.09/ √0.1633*0.8367( 1/200 + 1/400)

z= 0.301/√ 0.13663( 3/400)

z= 0.301/0.0320

z= 9.406

The calculated value of z falls in the critical region therefore we reject the null hypothesis and conclude that the 10% significance level that the scrap rate of the new method is different from the old method.

Answer:

i am having issues using the math editor and my time is almost running out. i added an attachment.

Step-by-step explanation:

Answer:

10

Step-by-step explanation:

f(o) is given when x= 0 in f(x)

f(0) = 5 ( 0 + 2 ) 2 - 10

= 20 - 10

= 10

Answer:

[tex] \boxed{ \bold{ \huge{ \sf{f{(0) = 10}}}}}[/tex]

Step-by-step explanation:

Given, f ( x ) = 5 ( x + 2 )² - 10

Let's find f ( 0 ) :

[tex] \sf{f(0) = 5( {0 + 2)}^{2} - 10}[/tex]

Add the numbers

⇒[tex] \sf{f(0) = 5( {2)}^{2} - 10}[/tex]

Evaluate the power

⇒[tex] \sf{f(0) = 5 \times 4 - 10}[/tex]

Multiply the numbers

⇒[tex] \sf{ 20 - 10}[/tex]

Subtract 10 from 20

⇒[tex] \sf{10}[/tex]

Hope I helped !

Best regards !!

Answer:

D question,somewhat confusing, itsit's like simultaneous equation,but values are different

Answer:

x = 4 + 2y/3

Step-by-step explanation:

Answer:

.02

Step-by-step explanation:

2 is in "Hundredths' place in .826

So, the number is multiplied with 1/100 or .01

=> 2 x 1/100

=> 2/100

=> .02

=> 2 x .01

=> .02

The value of 2 in .826 is .02

Answer:

  (3ab)/(2(b-a))

Step-by-step explanation:

The n-th term of an arithmetic progression is ...

  an = a1 +d(n -1)

Then the value of n is ...

  n = (an -a1)/d +1

The sum of an arithmetic progression is the product of the number of terms and the average of the first and last terms. In this sequence, the common difference d is ...

  d = (b -a)

So, the sum is ...

  Sn = (a +2a)/2·((2a -a)/(b -a) +1)

  Sn = (3ab)/(2(b-a)) . . . . sum of the arithmetic progression

__

Example:

The sequence 1, 1.5, 2 has ...

  a = 1, b = 1.5

Its sum is given by the above formula as ...

  Sn = 3(1)(1.5)/(2(1.5 -1)) = 4.5/(2(.5)) = 4.5 = 1 + 1.5 + 2 . . . . yes

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▹ Answer

1 - 9/7n

▹ Step-by-Step Explanation

1/7 - 3(3/7n - 2/7)

Remove the parentheses (Distribute -3 among the parentheses):

1/7 - 9/7n + 6/7

Calculate:

1 - 9/7n

Hope this helps!

CloutAnswers ❁

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Answer:

1-9/7n

Step-by-step explanation:

[tex]\frac{1}{7}-3(\frac{3}{7}n-\frac{2}{7} ) \\=\frac{1}{7}-\frac{9}{7}n +\frac{6}{7} \\=\frac{1-9n+6}{7} \\=\frac{7-9n}{7}\\=1-\frac{9}{7}n[/tex]