The size of a computer monitor is usually measured along the diagonal. An 18-in. rectangular monitor has a height of 9 in.What is the length of base of the monitor, to the nearest tenth of an inch?Enter your answer as a decimal in the box. __ in.

To solve this problem, you need to use the following equation:
a^2 + b^2 = c^2 
the diagonal of your equation is c, while either a or b can be your length or width. 
once you've decided which letter will be the length (the 9 inches), you will put those numbers into your equation and solve for you other letter.
9^2 + b^2 = 18^2
once youve solved for b, you will find that the answer is 15.6 inches
let me know if you want to see the steps of how i solved equation
:)