Four years from now, Rohan will be twice as old as he was 7 years ago. What is Rohan's present age?

Explanation

1. 01

   Let his present age be $x$.

2. 02

   $x + 4 = 2(x - 7)$, so $x + 4 = 2x - 14$.

3. 03

   $x = 18$. Check: in 4 years he is 22; 7 years ago he was 11; $22 = 2 \times 11$.