Perimeter = 2L + 2W = 256
"8 feet longer than it is wide"
translates to
L = 8 + W
we plug that into the first equation and get
2(8 + W) + 2W = 256
now we solve for W
distribute the 2
16 + 2W + 2W = 256
add like terms
16 + 4W = 256
subtract 16 from both sides
4W = 240
divide both sides by 4
W = 60
plug that into
L = 8 + W
and solve for L now
L = 8 + 60
so
L = 68
therefore your
length = 68
and
width = 60