Question

A box without a top is made from a rectangular piece of cardboard, with dimensions 25 inches by 20 inches, by cutting out square corners with side length x inches.
Which expression represents the volume of the box in terms of x?

Answer 1

To the risk of sounding redundant.

check the picture below.

Answer 2

When the corner is cut to a dimension of x, then the flap folded up, its height will be x. The appropriate choice is the last one, ...
  (25 -2x)(20 -2x)x