Question

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. Select the system equations that represents the problem.
J - 2M = 0
M - 2J = 0
J + M = 21
J = M + 2

Answer 1

This is similar to the previous one.

Answer 2

Can you tell me what answer you got?

Answer 3

??

Answer 4

j-2m = 0

Answer 5

Hint: Try forming an algebraic expression for the sum of their ages.

Answer 6

Isn't it J + M = 21?