1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Dimas [21]
3 years ago
9

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

Mathematics
1 answer:
lesya692 [45]3 years ago
6 0
J=john
m=mary
j is 2 times as old as mary
j=2 times m

sum is 21
m+j=21
find mary
subsitute

j=2m therefor subsitute 2m for j
m+2m=21
add like terms
3m=21
divide by 3
m=7

mary=7

*HOPE I HELPED!*
You might be interested in
Which equation represents the line that is perpendicular to and passes through (-40,20)?
emmasim [6.3K]

The equation of the perpendicular line to the given line is: y = -5/4x - 30.

<h3>What is the Equation of Perpendicular Lines?</h3>

The slope values of two perpendicular lines are negative reciprocal of each other.

Given that the line is perpendicular to y = 4/5x+23, the slope of y = 4/5x+23 is 4/5. Negative reciprocal of 4/5 is -5/4.

Therefore, the line that is perpendicular to it would have a slope (m) of -5/4.

Plug in m = -5/4 and (x, y) = (-40, 20) into y = mx + b to find b:

20 = -5/4(-40) + b

20 = 50 + b

20 - 50 = b

b = -30

Substitute m = -5/4 and b = -30 into y = mx + b:

y = -5/4x - 30

The equation of the perpendicular line is: y = -5/4x - 30.

Learn more about about equation of perpendicular lines on:

brainly.com/question/7098341

#SPJ1

8 0
1 year ago
PLEASE HELP ME !!!!!!!!!!!!!!!!!!
asambeis [7]
The solution is indeed accurate.
4 0
3 years ago
Read 2 more answers
The radius of a circular rug is 5 feet. How much ribbing will you need to buy to go around the
leonid [27]

The length around the rug is the circumference.

The formula is C = 2 x PI x r

C = 2 x 3.14 x 5 = 31.4 feet

5 0
3 years ago
Read 2 more answers
The simplified formula for calculating monthly lease payment is:
Effectus [21]

Answer:

depreciation fee + finance fee APEX

5 0
3 years ago
Can someone please help me find the rate of change in this function?
eimsori [14]

Answer:

If the answer isn't 0 or .0 I'm going to need some answer choices.

Step-by-step explanation:

4 0
2 years ago
Other questions:
  • Doug digs a hole that is 1.7 feet below ground level. He plants a bush that is 3 2/10 feet tall from the bottom of the root to t
    7·1 answer
  • melissa has 175 pictures to put in her scrapbook. each page holds 8 pictures. How many pages can she fill completely
    5·2 answers
  • Please help picture is there
    12·1 answer
  • Acording to what the harder you pedal a bicycle thr faster it will go
    7·2 answers
  • What will be the new position of the given point after rotating 180 about the origin
    14·2 answers
  • For the equation y = 2x^2 − 5x + 18, choose the correct application of the quadratic formula.
    7·1 answer
  • What is the surface area of a square with radius 4?
    9·2 answers
  • Convert 20 quarts to gallons. There are 4 quarts in a gallon.
    11·2 answers
  • Please hurry I’m timed! :c Who were the forty-niners?
    5·1 answer
  • How can the figure below be changed so that it has exactly one lines of symmetry?
    14·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!