I'm stuck on my math homework. Need help! Please solve!

Answers:
=========================================================
Explanation:
s = Sam's age right now
2s = the mother's age right now, since she is twice as old as Sam currently.
In 12 years time, Sam will be s+12 years old.
12 years ago from this current year, the mother was 2s-12 years old.
Since we're told these future and past ages line up, this means s+12 and 2s-12 are the same value
Set the expressions equal to one another and solve for s.
s+12 = 2s-12
s-2s = -12-12
-s = -24
s = 24
Sam is currently 24 years old.
His mother is currently 2s = 2*24 = 48 years old.
12 years ago, his mother was 2s-12 = 48-12 = 36 years old.
12 years from now, Sam will be s+12 = 24+12 = 36 years old.
Since we get 36 each time, this confirms we have the correct answers.