63 + 7
63 + 9
78 + 2
78 + 6
54 + 8
62 + 9
6 + 75
8 + 46
63 + 7 = 70
63 + 9 = 63 + 7 + 2 = 70 + 2 = 72
78 + 2 = 80
78 + 6 = 78 + 2 + 4 = 80 + 4 = 84
54 + 8 = 54 + 6 + 2 = 60 + 2 = 62
62 + 9 = 62 + 8 + 1 = 70 + 1 = 71
6 + 75 = 1 + (5 + 75) = 1 + 80 = 81
8 + 46 = 4 + (4 + 46) = 4 + 50 = 54