| 12 | ( | 80 | − | t | ) | = | 12 | ( | t | − | 56 | ) |
| 方程左边 = | 12 | × | 80 | − | 12 | t |
| = | 960 | − | 12 | t |
| 960 | − | 12 | t | = | 12 | ( | t | − | 56 | ) |
| 方程右边 = | 12 | t | − | 12 | × | 56 |
| = | 12 | t | − | 672 |
| 960 | − | 12 | t | = | 12 | t | − | 672 |
| - | 12 | t | − | 12 | t | = | - | 672 | − | 960 |
| - | 24 | t | = | - | 672 | − | 960 |
| - | 24 | t | = | - | 1632 |
| 1632 | = | 24 | t |
| 24 | t | = | 1632 |
| t | = | 1632 | ÷ | 24 |
| = | 1632 | × | 1 24 |
| = | 68 | × | 1 |
| t | = | 68 |