Since the total length of the wire is 26m, then 26m is the perimeter of the rectangle. Knowing that the perimeter of a rectangle is P = 2L + 2W
you'll have it as: 2L + 2W = 26..
divide the whole equation by 2 you'll have:
L + W = 13 ----equation 1..
Since the length is 3m longer than the width then you'll have it as:
L = W + 3 ----equation 2..
Substitute equation 2 to equation 1.
L + W = 13
W+3 + W = 13
substitute to equation 2..
L = W + 3