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

What Percent Of 700 Is 385

Cory's average score after 8 tests is 91%. If he gets a 78% on his 9th test what will his new average be? How do i figure out this problem?

write the ratio as a fraction in simplest form. 16ft to 6yd

K stands for a whole number. K + 7 is greater than 100 K - 7 is less than 90 Write all the numbers that k could be. Please help me

can humans cause a imbalance in the food chain

How do round, spiral, and rod-shaped bacteria look like?

write the ratio as a fraction in simplest form. 16ft to 6yd

Cory's average score after 8 tests is 91%. If he gets a 78% on his 9th test what will his new average be? How do i figure out this problem?

A cable is lifting a construction worker and a crate. The weights of the worker and crate are 965 N and 1510 N, respectively. The acceleration of the cable is

You just priced what it would cost to buy vinyl floor tiles at the local tile store. They quoted you $3.29 per tile. When you went home you found the same exact