Six years ago, Arjun was four times as old as his niece Bhavna. Six years from now, he will be twice as old as her. By how many years is Arjun older than Bhavna?

Explanation

1. 01

   Let Bhavna be $b$. Six years ago: $a - 6 = 4(b - 6)$, so $a = 4b - 18$.

2. 02

   Six years ahead: $a + 6 = 2(b + 6)$, so $4b - 12 = 2b + 12$.

3. 03

   $b = 12$, $a = 30$.

4. 04

   Difference = $30 - 12 = 18$ years.