P = 2L + 2W You are given L=12in and P=6L: 6L = 2L + 2W 4L = 2W 4*12 = 2W W = 24in Check (calculate Perimeter both ways): P = 2L + 2W = 2*12 + 2*24 = 24 + 48 = 72 P = 6L = 6*12 = 72 (ok)