You can write the dimensions of the rectangle as (x + 2) and (x - 5), and because the area is base × height, you can multiply the brackets together and make it equal to 56:
(x + 2)(2x - 5) = 56
2x² + 4x - 5x - 10 = 56
x² - x - 10 = 56
Now because you have an x², you need to make the equation equal to 0 so you can factorise, so:
2x² - x - 10 = 56
- 56
2x² - x - 66 = 0
(x - 6)(2x + 11)
So x is 6, because the other option is -5.5 and you cannot have a negative length.
I hope this helps!
