1st Equation:
8 × 9 = 72
33 + 72 = 105
The answer is 105
2nd Equation:
31 - 20 = 11
11 × 3 = 33
The answer is 33
3rd Equation:
102 - 6 = 8 - 5
102 - 6 = 96
96 = 8 - 5
8 - 5 = 3
96 = 3
93 = 3 is false so therefor, this equation has no solution.
4th Equation:
102 = 12 + 4 × 7 - 2
4 × 7 = 28
102 = 12 + 28 - 2
12 + 28 = 40
102 = 40 - 2
40 - 2 = 38
102 = 38
102 = 38 is false so, it means that this equation has no solution.