The perimeter of the rectangle is 14 feet, and the area is 12 square feet. What is the width of the rectangle?

I only have one example to go by and I don't get how it works with this problem.

2 (l + w) = 14
lw = 12

l + w = 7
w= 7 - l

l (7 - l) = 12
-l^2 + 7 l = 12
7 l - l^2 = 12

l^2 - 7l = 12
l^2 - 7l - 12 = 0
(l-3) (l-4) =0

l = 3 or 4

hope that helped

Adam