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

A cable is 40 decimeter a long. How long is the cable in meters.

A 100 pound person on earth would weigh about 4*4*4*4pounds on Jupiter. Evaluate the expression to determine how much a 100 pound person would weighing jupiter

is it true or false that Relations with the Native Americans remained cordial as the English settlements spread westward.

How much more money do 10 T-shirts cost that 6 T-shirts? Explian how you found your answer.

what is 555000 rounded to the nearest ten thousand

in which ways did taft helped conservation efforts and child labor problems

Which is an effective way to resist peer pressure to do something you're uncomfortable doing?

World War II was one of the most significant events of the 1900s and one of the most important events in US history. Think about how much the United States chan

how do bases bond together

Scientists believe that early human beings may have originated in