Question 258165
The formula for perimeter is
(i) P = 2L + 2w
we also know that 
(ii) w = (1/2)L + 2
by substitution, we get
(iii) {{{40 = 2L + 2((1/2)L + 2)}}}
(iv) {{{40 = 2L + L + 4}}}
(v) {{{36 = 3L}}}
L = 12
This means w = 8.