Tom's and tim's ages add up to 21 years. In 3 years, Tom will be twice time's age. How old are they now?

X=Tom's age

y=Tim's age.

we suggest this system of equations:

x+y=21

(x+3) = 2 (y+3)

We solve this system of equations by susbstitution method.

x=21-y

[ (21-y) + 3]=2 (y+3)

24-y=2y+6

-y-2y=6-24

-3y=-18

y=-18/-3=6

x=21-y

x=21-6=15.

Answer: Tom is 15 years old, and Tim is 6 years old.