Puzzle No.39/Solution

The Age Problem

Let M = Mary's age

2/3 x 2M/3 + 5 = 1M/2

4M/9 + 5 = 1M/2

5 = 1M/2 -4M/9

5 = 9M/18 - 8M/18

5 = 1M/18

1M = 90

So Mary is also 90 years old.