Please show me how to set this up and how to solve:

A ribbon with straight edges has an area of 24 inches squared. Its width is x and its length is 2x + 13. What is the width of the ribbon in inches?

x(2x+13) = 24

2x^2 + 13x - 24 = 0
(2x - 3)(x + 8) = 0
x = 3/2 or x = a negative, which is silly

the width is 3/2 or 1.5 inches
(length is 16 inches)