John is twice as old as Mary. The sum of thelr ages is 21. How old Is Mary?

Answers

Answer 1

Answer:   7 years

Step-by-step explanation:

let x be the age of Mary

so John's age will be 2x

the equation becomes

2x+x=21

3x=21

x=21/3

x=7

Answer 2

Answer:

Step-by-step explanation:

Let Mary's age = x years

John's age = 2 * x = 2x

The sum of their ages = 21

x + 2x = 21

3x = 21

Divide both sides by 3

x = 21/3

x = 7

Mary's age = 7 years


Related Questions

While in France, Judy wants to sign up for a bike tour to see the countryside. She likes a tour that is 40 kilometers long, but she isn't sure how far that is. She decides to estimate the distance in miles. If Judy uses the fact that 1 kilometer is about 0.6 miles, what will her estimate be?

Answers

Answer:

24 Miles

Step-by-step explanation:

We multiply:

40 * 0,6 = 24 miles

22/9 divided by 8, please hurry test is timed!

Answers

Answer:

0.30(5)

the 5 is repeating

Step-by-step explanation:

calculator

Alicia is a music artist. Her income can be represented by the function, f(a) = 200 + 12a, where a represents the total number of albums sold.

What is an acceptable domain for this situation?

Answers

Answer:

The answer is below

Step-by-step explanation:

A function shows the relationship between the set of inputs (independent variable) to the set of outputs (dependent variables).

The domain of a function is the set of possible inputs (independent variable) that satisfies the functions.

From the question, the domain of the function is the set of all possible vales of the inputs which is a (number of album sold).

Hence the domain of the function is:

0 < a < ∞

Help please I would really appreciate it thank you so much

Answers

Answer:

12 in the first blank

20 in the second one

Step-by-step explanation:

12 because it is 8+4

20 because it is 60/3

Each month, Kelsey donates 1/5 of her allowance to her school for supplies. 1/2 of that amount goes to the chorus class. How much of her allowance goes to supplies for the chorus class?
Please show your work.
Thank you :)

Answers

every month 1/10 of her allowance goes to chores class because 1/5x1/2 = 1/10 or 1/2 of 1/5 is 1/10

What is the distance between point P and point R?

Answers

Answer:

PR = 10

Step-by-step explanation:

PR = [tex]\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}[/tex]

The coordinates for P and R are (0,4) and (-6,-4) respectively.

So you plug in the values:

PR = [tex]\sqrt{(-6-0)^2+(-4-4)^2}[/tex]

PR = [tex]\sqrt{(-6)^2+(-8)^2}[/tex]

PR = [tex]\sqrt{36+64}[/tex]

PR = [tex]\sqrt{100}[/tex]

PR = 10

The function rule C = 40n + 210 relates the number of months n to cost in dollars C of a phone plan and budget phone. Make a table of the input/output pairs to show the cost of the phone and phone plan after 2, 12 and 24months

Answers

The cost of the the phone and phone plan after 2, 12 and 24months is $290, $690 and $1170 respectively.

What is a linear equation?

A linear equation is in the form:

y = mx + b

Where y,x are variables, m is the rate of change and b is the initial value of y.

Given the equation:

C = 40n + 210

Where C is the cost of a phone plan for n number of months.

After 2 months; C = 40(2) + 210 = 290

After 12 months; C = 40(12) + 210 = 690

After 24 months; C = 40(24) + 210 = 1170

The cost of the the phone and phone plan after 2, 12 and 24months is $290, $690 and $1170 respectively.

Find out more on linear equation at: https://brainly.com/question/14323743

Help pls!!!!!!!!!!!!! trigonometry is it cos sin or tan

Answers

Answer:

tan (angle T) = 5/2

angle T = arctan (5/2)

Which of the following systems of linear inequalities is represented by the solution graphed below?

Answers

The answer to this question is option A.

Please helppppppp meeee

Answers

Answer:

angle K is 30 degrees

Step-by-step explanation:

A triangle adds up to 180 degrees. since LM and KM are congruent angle L and M are both 75 degrees each you subtract from 180 and you get 30 degrees

How to solve for "Find the equation of the line that is perpendicular to y = -2/3x and contains point (4,-8)" ?

Answers

Answer:

[tex]y=\frac{3}{2}x+(-14)[/tex]

Step-by-step explanation:

Equation of a line has been given as,

[tex]y=-\frac{2}{3}x[/tex] --------(1)

Slope of the line is,

[tex]m_1=-\frac{2}{3}[/tex]

By the property of perpendicular lines,

If the two lines having slopes [tex]m_1[/tex] and [tex]m_2[/tex] are perpendicular to each other, [tex]m_1\times m_2=-1[/tex]

Therefore, slope of the line perpendicular to the line (1) will be,

[tex]-\frac{2}{3}\times m_2=-1[/tex]

[tex]m_2=\frac{3}{2}[/tex]

If this line passes through a point (4, -8) equation of the line will be,

[tex]y-y'=m_2(x-x')[/tex]

[tex]y+8=\frac{3}{2}(x-4)[/tex]

[tex]y=\frac{3}{2}x-6-8[/tex]

[tex]y=\frac{3}{2}x-14[/tex]

How do you find the equation of a line of a triangle when given the area and one set of coordinates?

Answers

The straight line through two points will have an equation in the form y = m x + c . We can find the value of , the gradient of the line, by forming a right-angled triangle using the coordinates of the two points.

2 sin2 (π/2 sin2x)=1+cos(π×cos2x)

Answers

Answer:

3/5Step-by-step explanation:

[tex]the \: equation \: is \: equivalent \: to \\ 2 \: { \sin }^{2} (( \: \frac{\pi}{2}) \: {cos}^{2} x ) = \\ \: 2 \: {sin}^{2} (( \frac{\pi}{2} sin \: 2x \: ) \\ = {cos}^{2} x = sin \: 2x \\ = \: \cos \: x(cos \: x \: - \: 2 \: sin \: x) \: = \: 0 \\ = \: 1 - 2 \tan \: x = 0 \: as \: cos \: x \: ≠ 0 \\ x ≠ (2n + 1) \frac{\pi}{2} \\ = \tan(x) = \frac{1}{2} \\ = \cos(2x) = \frac{1 - {tan \: }^{2}x }{1 + {tan \: }^{2} \:x } = \frac{3}{5} [/tex]

HOPE IT HELPS!!!!

If it is correct mark as BRAINLIEST ✌️

SOMEBODY PLEASE HELP

Answers

Answer:

x=40

Step-by-step explanation:

1/5x=8

x=8*5=40

x=40

9r^6/ 5r^3g^2, 5n^5c^-6 times 2n^-5c^3, and 9g^-4yA^4/3g^6y^-2 using properties of exponents, all this for 10 points

Answers

Answer:

Step-by-step explanation:

5n⁵c⁻⁵ *  2n⁻⁵c³ = (5*2)*n⁵⁺⁽⁻⁵⁾ * c⁻⁶⁺³

                          =10*n° *c⁻³

                           = 10c⁻³               (n° = 1}

[tex]a^{m}*a^{n}=a^{m+n}\\\\\frac{a^{m}}{a^{n}}=a^{m-n}\\\\\\\frac{9r^{6}}{5r^{3}g^{2}}=\frac{9}{5g^{2}}*r^{6-3}\\\\=\frac{9r^{3}}{5g^{2}}\\\\\\\\\frac{9g^{-4}y^{4}}{3g^{6}y^{-2}}=\frac{9}{3}*g^{-4-6}*y^{4-(-2)}\\\\=3*g^{-10}*y^{4+2}\\\\=3g^{-10}*y^{6}\\\\=\frac{3y^{6}}{g^{10}}[/tex]

A regular hexagon is to be cut out of a circular sheet of metal that has a radius of 6
inches.

Approximately how many square centimeters of sheet metal will be left over as
scraps?
A. 32.9 square centimeters
B. 93.5 square centimeters
C. 113.1 square centimeters
D. 126.2 square centimeters

Answers

The correct answer to your problem would be “d”

Pls help ..
if A =
[4 3] is a singular matrix, find 'a'
[ a 3]​

Answers

Answer:

a = 4.

Step-by-step explanation:

We know that:

[tex]A = \left[\begin{array}{ccc}4&3\\a&3\end{array}\right][/tex]

is a singular matrix, now we want to find the value of a.

We know that a matrix is singular if:

Det [A] = 0

Where remember that the determinant of a 2x2 matrix is given by:

[tex]M = \left[\begin{array}{ccc}k_{11&k_{12\\k_{21}&k_{22}\end{array}\right]\\\\det[M] = k_{11}*k_{22} - k_{12}*k_{21][/tex]

Then the determinant of A is:

Det [A] = 4*3 - a*3

and that must be zero, so:

4*3 - a*3 = 0

Now we just need to find the value of a:

12 - a*3 = 0

12 = a*3

12/3 = a

4 = a

So the value of a is 4.

what is the gradient of line Y =-3×+5​

Answers

Gadient: -3
The form: y=ax+b
a: gadient
b: intercept

7.80/hour=________ cents/minute?

Answers

Answer: 0.13 cents per minute.

Step-by-step explanation:

7.80 divided by 60(min per hour.)= .13 cents.

1$ = 100 cents, 1 hour = 60 minutes

$7.80/hour = (7.8*100) cents / (1*60)minutes

= 780 cents/60 minutes

= 13 cents/minute

How much is 3 lbs of gold worth I’m American money

Answers

Answer:

$1865

The gold calculator is a gold melt value calculator which can be used to determine the value of gold metal inside an item with a known weight and gold purity. These items may include gold jewelry (such as, bangles, bracelets, chains, earrings, necklaces, pendants, and rings), gold bullion and gold coins.

The gold calculator is designed to calculate the gold metal value for one item at a time. If you would like to calculate the gold metal value for multiple items simultaneously consider using the scrap gold calculator for scrap gold, the gold bullion calculator for gold bullion bars and coins, and the gold coin calculator for gold coins.

Divide. Round to the nearest tenth.
104 divided by 1.5

Answers

Answer:

70

Step-by-step explanation:

too easy

Please help I’ll give brainllist

Answers

The answer is C :) hope this helps
5 mph I’m pretty sure x

Elizabeth sells popcorn to the students at the annual school dance. She pays $30.00 to rent the popcorn maker and $0.75 in supplies for each bag of popcorn. If Elizabeth buys supplies for p bags of popcorn, which equation expresses her total cost, c, in dollars?

Answers

Answer:

c = $30 + $0.75p

Step-by-step explanation:

total cost = total fixed cost + total variable cost

total fixed cost = $30

Fixed costs are costs that do not vary with output.

total variable cost = variable cost per unit x total unit

p x 0.75

Variable costs are costs that vary with production

23. About how much would 4 horses weigh? Write the weight two different ways.​

Answers

An average horse weighs 900-2,000 pounds, depending on size and breed. A lean, racing fit Thoroughbred, for example, has an average weight of 900-1,100 pounds, while the average Clydesdale (think Budweiser) weighs in at 1,800-2,000 pounds

Answer:

If one horse will weigh about 2000 pounds, or 1000kg, then four horses will weigh about 8000 pounds or 4000kg

Drag the tiles to the correct boxes to complete the pairs. Not all tiles will be used. Match the questions with their solutions. 5 80 6 200 8 150 Joshua has 11 baskets of apples. In total, he has 88 apples. How many apples are there in 1 basket? arrowRight Mindy can type 40 words per minute. How many words can she type in 5 minutes? arrowRight Jessica had 20 balloons, which she distributed among 4 of her friends. How many balloons did each friend get? arrowRight Max can make 1 greeting card in 5 minutes. How many greeting cards can he make in 30 minutes? arrowRight

Answers

Answer:

1.) 8 ; (2.) 200 ; (3.) 5 ; (4.) 6

Step-by-step explanation:

1.)

Number of apple baskets = 11

Total number of apples = 88

Number of apples per basket = 88 / 11 = 8

2).

Number of words per minute = 40

Number of words that can be typed in 5 minutes :

40 * 5 = 200 words

3.)

Number of balloons = 20

Number of friends = 4

Number of balloons per friend = 20/4 = 5

4.)

Time required to make 1 greeting card = 5 minutes

Number of greeting cards that can be made in 30 minutes :

30 minutes / 5 minutes = 6 greeting cards

Given that AABC~ ADEF, solve for x.​

Answers

Answer:

D.7

because in similar triangle the corresponding sides are proportional

Step-by-step explanation:

30/5 =42/X

Criss cross and X=(42X5)/30=7

The value of x will be,

⇒ x = 7

What is mean by Triangle?

A triangle is a three sided polygon, which has three vertices and three angles which has the sum 180 degrees.

Given that;

Triangles ABC and DEF are similar.

Now, By definition of proportionality we get;

⇒ AB / BC = DE / EF

⇒ 30 / 42 = 5 / x

⇒ 30x = 5 × 42

⇒ 30x = 210

⇒ x = 210 / 30

⇒ x = 7

Thus, The value of x will be,

⇒ x = 7

Learn more about the triangle visit;

brainly.com/question/1058720

#SPJ7

simplify

x - ( - 6 x )​

Answers

Answer:

7x

Step-by-step explanation:

Answer:

answer

x - ( - 6x )

x + 6x

= 7x

which equation has the steepest graph?
A. y=7x+3
B. y=8x-1
C. y=-10x-4
D. y=-2x+6

Answers

The answer to this question would be C. Y=-10x-4

Which of the following graphs represent the dilation of
the given triangle XYZ with the center of dilation at the
origin with a scale factor 3?


Please I need it fast

Answers

Answer:

12y

Step-by-step explanation:

Please help will be marked as brainliest if correct

Answers

Answer:

I think the answer is three.

Here is a picture of my work. The answer is 3. Hope this helps:)
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