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
J = M + 2
M - 2J = 0
J + M = 21

Correct answers are:

J + M = 21

J - 2M = 0

d

step-by-step explanation:

the solution is in the picture

the statemwnt is the company makes small and large snow cone cups.

large=it holds more then the small

small=it holds less then the large