8 • 9 – 7 • 8 = 72 – 56 = 16;
6 • 5 + 5 • 6 = 30 + 30 = 60;
74 – 35 + 18 = 39 + 18 = 57;
68 + 15 – 44 = 83 – 44 = 39;
99 – 10 • 9 = 99 – 90 = 9;
8 • 0 + 8 • 8 = 0 + 64 = 64.