| ( | 121 | − | x | ) | ÷ | 10 | = | ( | 185 | − | x | ) | ÷ | 15 |
| 方程左边 = | 121 | × | 1 10 | − | x | × | 1 10 |
| = | 121 10 | − | x | × | 1 10 |
121 10 | − | 1 10 | x | = | ( | 185 | − | x | ) | ÷ | 15 |
| 方程右边 = | 185 | × | 1 15 | − | x | × | 1 15 |
| = | 37 3 | − | x | × | 1 15 |
121 10 | − | 1 10 | x | = | 37 3 | − | 1 15 | x |
| - | 1 10 | x | + | 1 15 | x | = | 37 3 | − | 121 10 |
| - | 1 30 | x | = | 37 3 | − | 121 10 |
| - | 1 30 | x | = | 7 30 |
| - | 7 30 | = | 1 30 | x |
1 30 | x | = | - | 7 30 |
| x | = | - | 7 30 | ÷ | 1 30 |
| = | - | 7 30 | × | 30 |
| = | - | 7 | × | 1 |
| x | = | - | 7 |