This is a sample page from the math facts fluency challenge that I give my 3rd graders. There are 8 levels in all. This second level tests students' subtraction math facts to 20.
You can use this as a timed test, or just simply as extra homework practice. The file is an Excel worksheet and can easily be edited so YOU WILL NEVER NEED ANOTHER subtraction math facts worksheet again. to get an entirely new set of 50 problems, simply change/edit any cell (even a blank one). The math facts problems will automatically change themselves.