| 13 | ( | 80 | − | t | ) | = | 11 | ( | t | − | 56 | ) |
| 方程左边 = | 13 | × | 80 | − | 13 | t |
| = | 1040 | − | 13 | t |
| 1040 | − | 13 | t | = | 11 | ( | t | − | 56 | ) |
| 方程右边 = | 11 | t | − | 11 | × | 56 |
| = | 11 | t | − | 616 |
| 1040 | − | 13 | t | = | 11 | t | − | 616 |
| - | 13 | t | − | 11 | t | = | - | 616 | − | 1040 |
| - | 24 | t | = | - | 616 | − | 1040 |
| - | 24 | t | = | - | 1656 |
| 1656 | = | 24 | t |
| 24 | t | = | 1656 |
| t | = | 1656 | ÷ | 24 |
| = | 1656 | × | 1 24 |
| = | 69 | × | 1 |
| t | = | 69 |