Homeschool worksheets are far more than busy work. They are an important part of making sure that the concepts you teach in your home school stick with your child. Just make sure you have a good source for providing the worksheets, and that they're the right ones for your kid or kids.
Review subtraction of 2 numbers whose sums would be 18 or less
Save Money : It's easy to see how free worksheets can save you money. If you want, you can skip buying math books and just use worksheets that you get for free on the internet. All you need to do is use a "scope and sequence" book that tells you what your child needs to be doing in math by age and grade. This book is essential when you homeschool.
Another important point I keep in mind is that I never want this regular math review time to take up and hour of class time. I want it to be quick but effective. This is not instructional time, but time for the students to review material they have already learned.