6 − 2 = 4 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14   7 − 1 = 6 9 + 7 = 1 + 6 = 10 + 6 = 16   8 − 4 = 4 6 + 8 = 6 + 4 + 4 = 10 + 4 = 14   9 − 3 = 6 7 + 9 = 7 + 3 + 6 = 10 + 6 = 16