| ( | 68 | − | 41 | ) | ÷ | ( | 41 | − | 40 | ) | = | ( | 85 | − | t | ) | ÷ | ( | t | − | 71 | ) |
| 方程两边同时乘以: | ( | 41 | − | 40 | ) | , | ( | t | − | 71 | ) |
| ( | 68 | − | 41 | ) | ( | t | − | 71 | ) | = | ( | 85 | − | t | ) | ( | 41 | − | 40 | ) |
| 68 | ( | t | − | 71 | ) | − | 41 | ( | t | − | 71 | ) | = | ( | 85 | − | t | ) | ( | 41 | − | 40 | ) |
| 68 | ( | t | − | 71 | ) | − | 41 | ( | t | − | 71 | ) | = | 85 | ( | 41 | − | 40 | ) | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 68 | × | 71 | − | 41 | ( | t | − | 71 | ) | = | 85 | ( | 41 | − | 40 | ) | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 68 | × | 71 | − | 41 | ( | t | − | 71 | ) | = | 85 | × | 41 | − | 85 | × | 40 | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 4828 | − | 41 | ( | t | − | 71 | ) | = | 3485 | − | 3400 | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 4828 | − | 41 | ( | t | − | 71 | ) | = | 85 | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 4828 | − | 41 | t | + | 41 | × | 71 | = | 85 | − | t | ( | 41 | − | 40 | ) |
| 68 | t | − | 4828 | − | 41 | t | + | 41 | × | 71 | = | 85 | − | t | × | 41 | + | t | × | 40 |
| 68 | t | − | 4828 | − | 41 | t | + | 2911 | = | 85 | − | t | × | 41 | + | t | × | 40 |
| 27 | t | − | 1917 | = | 85 | − | 1 | t |
| 27 | t | + | 1 | t | = | 85 | + | 1917 |
| 28 | t | = | 85 | + | 1917 |
| 28 | t | = | 2002 |
| t | = | 2002 | ÷ | 28 |
| = | 2002 | × | 1 28 |
| = | 143 | × | 1 2 |
| t | = | 143 2 |
| t | = | 71.5 |