how do i find the width of a rectangle

Question

If the width of each rectangle is 3 inches longer than the length of each rectangle and each rectangle has an area of 12 square inches.  Find the length of each rectangle.  Find the area of all 3 rectangles.

Answer 1

If the length is x then the area is x(x+3)=12, so x^2+3x-12=0. So, using the formula, x=(-3+sqrt(9+48))/2=(-3+sqrt(57))/2=2.275" approx. The other root is negative so is inapplicable. We already have the area of one rectangle so the area of 3=3*12=36 sq in.