You have to multiply 18 by three which is 54 inches. then you have to divide 54 by 12 because a foot is 12 inches. when you do that you should get 4.5 then you subtract 4.5 by 5.5 and get 1 foot of rope left 18*3=54 54/12=4.5 5.5-4.5=1.0 1 foot of rope