You are measuring a board so you can cut it. You need to cut the wood from 1 1/4 to 1/2. How long is the piece of wood you are going to cut?
To determine the length of the piece of wood you are going to cut, you need to subtract 1/2 from 1 1/4.
1 1/4 - 1/2 = 5/4 - 2/4 = 3/4
Therefore, the length of the piece of wood you are going to cut is 3/4.