“Subtraction Flash Cards” set is a Sure and Effective Way to learn and practice Subtraction Facts up to 20. There are 40 both sides printed, divided into 2 levels, large Flash Cards. Each card has two sums printed in big and bold type and their answers on the back. Children first practice with Level 1 (sums up to 10) cards and then with Level 2 (up to 20) cards. To reinforce their understanding and test knowledge of subtraction they also play group games. This way the child learns in most interactive and enjoyable way.