| 30 | − | 3 | t | = | 2 | ( | 2 | t | − | ( | 30 | − | 3 | t | ) | ) |
| 方程右边 = | 2 | × | 2 | t | − | 2 | ( | 30 | − | 3 | t | ) |
| = | 4 | t | − | 2 | ( | 30 | − | 3 | t | ) |
| = | 4 | t | − | 2 | × | 30 | + | 2 | × | 3 | t |
| = | 4 | t | − | 60 | + | 6 | t |
| = | 10 | t | − | 60 |
| 30 | − | 3 | t | = | 10 | t | − | 60 |
| - | 3 | t | − | 10 | t | = | - | 60 | − | 30 |
| - | 13 | t | = | - | 60 | − | 30 |
| - | 13 | t | = | - | 90 |
| 90 | = | 13 | t |
| 13 | t | = | 90 |
| t | = | 90 | ÷ | 13 |
| = | 90 | × | 1 13 |
| t | = | 90 13 |
| t | = | 6.923077 |