Explicație pas cu pas:
91 - 9 × 0 = x + 4 × 7
91 - 0 = x + 28
x = 90 - 28
x = 62
x - 4 × 8 = 85 - 9 × 4
x - 32 = 85 - 36
x = 49 + 32
x = 81
4 × 8 + x = 9 × 9 - 27
32 + x = 81 - 27
x = 54 - 32
x = 22
x - 9 × 3 = 6 × 7 + 21
x - 27 = 42 + 21
x = 63 + 27
x = 90
x + 7 × 8 = 94 - 6 × 3
x + 56 = 94 - 63
x = 31 - 56
x = -25
6 × 9 + x = 6 × 4 + 8 × 8
54 + x = 24 + 64
x = 88 - 54
x = 34
x + 6 × 8 = 9 × 9
x + 48 = 81
x = 81 - 48
x = 33