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.