8 + 2 = 10 7 + 3 = 10 6 + 4 = 10 9 + 1 = 10 5 + 5 = 10   10 − 4 = 6 14 − 4 = 10 8 − 4 = 4 9 − 4 = 5 4 − 4 = 0