olume = length * height * width
Therefore 280 = 4 * (n + 2) * (n + 5)
Divide both sides of the equation by 4
70 = (n + 2)(n +5)
Expand
70 = n^2 + 5n + 2n + 10
Subtract 70 from both sides and simplify
0 = n^2 + 7n -60
Factor
(n +12)(n -5) = 0
Therefore n = -12 or + 5
As n cannot be less than -2 as you cannot have a negative dimension, it means that n = 5 and the sides are 4, (5 + 2), (5 + 5) = 4, 7 and 10 inches respectively
Volume is therefore
4*7*10 = 280 = correct
Hope this helped!
