Three years ago, Marry was three times as old as his brother. Five years from now he will be twice as old as his brother. How is Marry now?

3 years ago:

m - 3 = 3 (b - 3)

m - 3 = 3b - 9

m + 6 = 3b

m/3 + 2 = b

5 years from now:

m + 5 = 2 (b + 5)

m + 5 = 2b + 10

m - 5 = 2b

m/2 - 5/2 = b

combine:

m/3 + 2 = m/2 - 5/2

1. multiply by 6

2m + 12 = 3m - 15

2. add 15 - 2m to both sides

27 = m

Marry is 27 years old.