Find the missing side when an area is given

Question

I'm stuck on this problem and I've been trying to figure it out but I can't seem to grasp it, can anyone help?

One side of a rectangle is 6 cm longer than two times another side. The area of the rectangle is 56 cm2. Find the length of the longer side.

Answer 1

x(2x+6) = 56

2x^2 + 6x - 56 = 0

x^2 + 3x - 28 = 0

(x + 7)(x-4) = 0

x-4 = 0

x= 4

rectangle 4 by 14