If you don't use equations, you can actually draw the corresponding relationship at a glance. What is cut off is unknown, but when we look at the picture, A must be equal to B, and a+c=3b is also the same problem. Because a=b, A must take one copy and C must take two copies. C is the difference between two ropes, 63-29=34, one strand: 34÷2= 17, so the cut is 29- 17= 12.