What is 13 pound 7 oz minus 7 pound 13 oz?

Answer 1

The idea here is that, to be able to subtract the ounces, you "borrow" from the pounds. In other words, in 13 lb 7 oz, you take away one pound, and add the equivalent (16 ounces) to the 7 ounces. After doing this change, you can easily subtract.