The area of a rectangle is 56 cm. the length is 2cm more than x and width is 5 cm less than twice x. solve for x. round to the nearest whole number

Area = Length * Width = l * w
l = x + 2
w = 2x - 5
Area = (x + 2)(2x - 5) = 56
Area = 2x^2 -x  - 10 = 56
Area = 2x^2 - x - 66 = 0 Now you have to factor this thing.
Area = (2x + 11)( x - 6) = 0 This is more or less done by guessing. 
2x + 11 = 0 can't work. x would be negative.
x - 6 = 0
x = 6.

Check

l = x + 2
l = 6 + 2
l = 8

w = 2*x - 5
w = 2*6 - 5
w = 12 - 5
w = 7

l*w = 8*7 = 56. It checks.
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