The surface area of a box is 160 square inches. The length of the box is twice its width, and is 4 inches less than its height. What is the height of the box, in inches?

Let the width be x. Then the length is 2x, and the height is 2x + 4. This gives you the quadratic equation 12x^2 + 24x = 180.

The soluiton is x = 3, so the height is 2*3 + 4 = 10.