| 90 | = | 90 | − | ( | x | ÷ | ( | 24000000 | ÷ | 90 | ) | ) | + | 20 |
| 90 | = | 90 | − | x | ÷ | ( | 24000000 | ÷ | 90 | ) | + | 20 |
| 90 | = | 110 | − | x | ÷ | ( | 24000000 | ÷ | 90 | ) |
| 方程两边同时乘以: | ( | 24000000 | ÷ | 90 | ) |
| 90 | ( | 24000000 | ÷ | 90 | ) | = | 110 | ( | 24000000 | ÷ | 90 | ) | − | x |
| 90 | × | 24000000 | ÷ | 90 | = | 110 | ( | 24000000 | ÷ | 90 | ) | − | x |
| 90 | × | 24000000 | ÷ | 90 | = | 110 | × | 24000000 | ÷ | 90 | − | x |
| 24000000 | = | 88000000 3 | − | x |
| x | = | 88000000 3 | − | 24000000 |
| x | = | 16000000 3 |