These flashcards are designed to be able to print as double sided cards, with one addition fact on the front and the related subtraction fact on the back. In this way, students can learn about the three numbers within the fact family. Nine strategies are based on adding a number to ten - remove one from the other number to add to the nine and create a ten (ex. 9+4 = 9+1+3 = 10+3 = 13). Facts go from 0+9 / 9-0 to 9+10 / 19-10.