Sha7contubstewood Sha7contubstewood

03-02-2016
Mathematics

contestada

John is twice as old as Mary. The sum of their ages is 21. How old is Mary?
Let J = John's age and M = Mary's age.

Respuesta :

apologiabiology apologiabiology

03-02-2016

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

Answer Link

Otras preguntas

This LEGENDARY character made a much-celebrated comeback in 2017. What was the name of the villain he faced in this epic tale?

Which of the following was a key to the North winning the Civil War?

Essays are always formal.

Tanya has a garden with a trench around it .The garden is a rectangle with length 2 1/2m and width 2 m. The trench and garden together with length 3 1/2m and wi

Read this excerpt from "A Visit from the Goon Squad." That’s when he began singing the songs he’d been writing for years underground, songs no one had ever hear

How do I find the value of X ???

According to communication scholar william rawlins, friends who don't spend a lot of time together can still maintain a satisfying connection if

[CORRECT ANSWER RECEIVES BRAINLIEST ONLY The work of a student to solve a set of equations is shown: Equation A: y = 16 – 2z Equation B: 7y = 2 – 4z Step 1:

Suppose that there are two solid steel spheres. the second sphere has a radius twice as large as the radius of the first sphere.

perform the indicated operation 2 3/8 x 5 3/4