The numbers $2x$, $x + 3$, 17, 11, $x - 2$, 20 and 9 have a range of 25, where $x$ is a positive whole number. What is $x$?

Explanation

1. 01

   If $x - 2$ were the smallest, the largest would be at least 20 and the range would be $20 - (x - 2) = 22 - x$, and $22 - x = 25$ gives $x = -3$, impossible. So 9 is the smallest.

2. 02

   Then the largest is $9 + 25 = 34$. The biggest expression is $2x$, so $2x = 34$ and $x = 17$.

3. 03

   Check: 34, 20, 17, 11, 15, 20, 9 have range $34 - 9 = 25$.