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

E. E. Cummings was a painter as well as a poet. a. True b. False

Mass production requires all of the following except a. division of labor b. interchangeable parts c. assembly line d. training in each part of production

Positive visual environments can: a. motivate you b. relieve stress c. improve your mood d. all of the above

Please help with this problem!!! Asap thank u so much!!!

public opinion is influenced by the Home the school and other elements in the country

The scale on a map shows 5 Centimeters = 2 Kilometers. What number of centimeters on the map represents an actual distance of 5 kilometers?

If 560 mg is 80% of a dose of medicine how much is a full dose

True or false one of the benefits of using an exercise ball is generally involves the core muscles?

What is parliamentary democracy in your own words?? I don't accept answers from other websites.

What's the answer to this math problem