w =width
l = 2w+4
p= 7w-3
P = 2(l+w)
substitute in p = 7w-3 and l = 2w+4
7w-3 = 2(2w+4+w)
combine like terms
7w-3 =2(3w+4)
distribute
7w-3 = 6w +8
subtract 6w from each side
w-3 = 8
add 3 to each side
w = 11
l = 2w + 4
l = 2(11) + 4 = 22+4 = 26
P = 7w-3 = 7*11-3 = 77-3 = 74
