l = 2w + 4 , l + w = 80
solve using subsitiution.
(2w + 4) + w = 80
simplify / combine common
3w + 4 = 80
subtract 4 from both sides
3w = 76
divide by 3
w = 25 1/3 in
80 - 25 1/3 = 54 2/3
is it true that 54 and 2/3 inches is 4 inches more than two times 25 1/3? Yes.
Length = 54 and 2/3 inches
W = 25 and 1/3 inches
hope this helps ;D