Question

How do I solve for x?

Answer 1

So it states that the area of the rectangle is 56 cm, so all of it.
Given: 56 cm of rectangle
Unknown: find x
Length: 2 + x or x + 2
Width: 2x-5
Area = l * w
(x+2)(2x-5) 
set x equal to 0
x+2=0   --> x=-2                2x-5=0 --> 2x=5 --> x = 5/2
so the answer we got was x=-2,5/2
we know that x cannot be negative because you can't measure with negative numbers, therefore, 5/2 is your answer              

Answer 2

Length = a
width = b

ab = 56 ---- first equation
a = 2 + x ---- second equation
b = 2x - 5 ---- third equation

substitude second and third equation into the first equation

(2+x)(2x-5) = 56
4x - 10 + 2x^2 - 5x = 56
2x^2 - x - 10 - 56 = 0
2x^2 - x - 66 = 0
(x-6)(2x+11) = 0
x1 = 6 , x2 = - 11/2 ---> - 5.5 (nearest whole num)