a : 8 + 9
64 8 17 → 64 : 8 = 8; 8 + 9 = 17
32 4 13 → 32 : 8 = 4; 4 + 9 = 13
40 5 14 → 40 : 8 = 5; 5 + 9 = 14
72 9 18 → 9 × 8 = 72; 9 + 9 = 18
56 7 16 → 16 - 9 = 7; 7 × 8 = 56
