| 3 | ( | 55 | − | t | ) | = | 1 | ( | t | − | 40 | ) |
| 方程左边 = | 3 | × | 55 | − | 3 | t |
| = | 165 | − | 3 | t |
| 165 | − | 3 | t | = | 1 | ( | t | − | 40 | ) |
| 方程右边 = | 1 | t | − | 1 | × | 40 |
| = | 1 | t | − | 40 |
| 165 | − | 3 | t | = | 1 | t | − | 40 |
| - | 3 | t | − | 1 | t | = | - | 40 | − | 165 |
| - | 4 | t | = | - | 40 | − | 165 |
| - | 4 | t | = | - | 205 |
| 205 | = | 4 | t |
| 4 | t | = | 205 |
| t | = | 205 | ÷ | 4 |
| = | 205 | × | 1 4 |
| t | = | 205 4 |
| t | = | 51.25 |