| ( | 20 | ÷ | 60 | ) | = | ( | X | − | 697 | ) | ÷ | 63 |
| 方程左边 = | 20 | ÷ | 60 |
| = | 1 3 |
1 3 | = | ( | X | − | 697 | ) | ÷ | 63 |
| 方程右边 = | X | × | 1 63 | − | 697 | × | 1 63 |
| = | X | × | 1 63 | − | 697 63 |
1 3 | = | 1 63 | X | − | 697 63 |
| - | 1 63 | X | = | - | 697 63 | − | 1 3 |
| - | 1 63 | X | = | - | 718 63 |
718 63 | = | 1 63 | X |
1 63 | X | = | 718 63 |
| X | = | 718 63 | ÷ | 1 63 |
| = | 718 63 | × | 63 |
| = | 718 | × | 1 |
| X | = | 718 |