When Priya was born, her father was 28 years old. Today her father is five times as old as she is. In how many years from now will her father be exactly twice her age?

Explanation

1. 01

   Let Priya be $p$; father = $p + 28$. Then $5p = p + 28$, so $p = 7$ and father = 35.

2. 02

   After $t$ years: $35 + t = 2(7 + t)$.

3. 03

   $35 + t = 14 + 2t$, so $t = 21$.

4. 04

   Check: in 21 years they are 28 and 56.