| X | − | ( | ( | X | ÷ | 300 | ) | × | 40 | ) | − | 9 10 | X | = | 683 |
| 方程左边 = | 1 10 | X | − | ( | ( | X | ÷ | 300 | ) | × | 40 | ) |
1 10 | X | − | ( | ( | X | ÷ | 300 | ) | × | 40 | ) | = | 683 |
| 方程左边 = | 1 10 | X | − | ( | X | ÷ | 300 | ) | × | 40 |
| = | 1 10 | X | − | X | ÷ | 300 | × | 40 |
| = | 1 10 | X | − | X | × | 2 15 |
| = | - | 1 30 | X |
| - | 1 30 | X | = | 683 |
| - | 683 | = | 1 30 | X |
1 30 | X | = | - | 683 |
| X | = | - | 683 | ÷ | 1 30 |
| = | - | 683 | × | 30 |
| X | = | - | 20490 |