The width of a retangle is 2 ft. less than the lenghth. The area is 15ft^2. Find the length and th width.

What is the formula? Is it -b +-Sqr b^2 -4ac/2a. If not please show me the steps to solve this word problem.

You need to set up your variables first.

Let x be the shorter side, and y be the longer side.
We know that

x = y - 2
xy = 15

You have two equations with two unknowns. Solve simultaneously. Can you do this? :)