a + 7 × 5 = 9 × 9
a + 35 = 81
a = 81 - 35
a = 46
a + 4 × 4 = 8 × 7
a + 16 = 56
a = 56 - 16
a = 40
8 × 8 - a = 6 × 6
64 - a = 36
a = 64 - 36
a = 28
9 × 8 - a = 3 × 9
72 - a = 27
a = 72 - 27
a = 45
a - 5 × 6 = 9 × 7
a - 30 = 63
a = 63 + 30
a = 93
a - 3 × 8 = 7 × 6
a - 24 = 42
a = 42 + 24
a = 66