Call the width of the rectangle x. Call the length of the rectangle x + 2. The area of the rectangle would be the length times the width. We know this is 15 square inches. Set up the equation and solve for x.
(x +2)x = 15
x2 + 2x = 15
x2 + 2x - 15 = 0
Factor the quadratic equation:
(x - 3)(x + 5) = 0
x = 3 or x = -5
Since length can't be negative, discard the answer -5.
If x = 3, then the width is 3 and the length is x + 2 or 5. 5 x 3 = 15 which equals the area.