L * W = A.
L + 5 = W
Substitute (L + 5) for W in the first equation.
L(L + 5) = A = 456.
distribute the L.
L² + 5L = 456
L² + 5L - 456 = 0
(L + 24)(L - 19) =0
L= - 24 and L = 19.
Because 19 is positive L = 19.
Because 24 is 5 more than L and when multiplied by L = 456, W = 24.