Why just do math worksheets when you can make it a little more fun. I save every milk cap that enters this house (which is a lot because we are a milk drinking, cereal eating family of 6). There are so many things you can do with them. For this workbox I wrote the numbers 1-9 twice and placed them in a bucket. Jackson was working on 3 digit subtraction so I took a piece of notebook paper and went ahead and drew the problems with blanks. By doing this he knew how many he had to do, how many digits, and it lined them up for him. Notice the paper is turned sideways. This is a great trick I learned teaching 4th grade. The lines on the notebook paper act as guides to help them keep their numbers lined up. That alone eliminates most mistakes kids make when writing their own problems.
Jackson had to draw out 6 caps which became his problems.
I recommend telling them they have to write the numbers down as they draw them for the top but allow them to rearrange the lower numbers to make sure the bottom number is smaller than the top (another important skill!).
This is also obviously great for addition as well. We'll probably soon use it for multiplication too since that is our summer focus!