Here's a quick set of 60 flash cards to help with addition and subtraction.
Here's how they work: If you cover the big number (circled to indicate the sum), the other two have to be added to get a sum. If you cover either of the smaller numbers, you have to subtract the small one from the circled one to get the other number in the fact family.
Each page has 5 double-sided cards. Each side of the card has 3 problems on it, so that's 6 problems per card, and 30 per page. I have 12 pages of these! That's 360 math facts. It's nearly every combination of addition and subtraction math problem from 0-20.
There are also 2 blank printable pages for you to use to make your own fact cards.