| ( | 68 | − | 47 | ) | ÷ | ( | 47 | − | 40 | ) | = | ( | 85 | − | t | ) | ÷ | ( | t | − | 71 | ) |
| 方程两边同时乘以: | ( | 47 | − | 40 | ) | , | ( | t | − | 71 | ) |
| ( | 68 | − | 47 | ) | ( | t | − | 71 | ) | = | ( | 85 | − | t | ) | ( | 47 | − | 40 | ) |
| 68 | ( | t | − | 71 | ) | − | 47 | ( | t | − | 71 | ) | = | ( | 85 | − | t | ) | ( | 47 | − | 40 | ) |
| 68 | ( | t | − | 71 | ) | − | 47 | ( | t | − | 71 | ) | = | 85 | ( | 47 | − | 40 | ) | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 68 | × | 71 | − | 47 | ( | t | − | 71 | ) | = | 85 | ( | 47 | − | 40 | ) | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 68 | × | 71 | − | 47 | ( | t | − | 71 | ) | = | 85 | × | 47 | − | 85 | × | 40 | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 4828 | − | 47 | ( | t | − | 71 | ) | = | 3995 | − | 3400 | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 4828 | − | 47 | ( | t | − | 71 | ) | = | 595 | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 4828 | − | 47 | t | + | 47 | × | 71 | = | 595 | − | t | ( | 47 | − | 40 | ) |
| 68 | t | − | 4828 | − | 47 | t | + | 47 | × | 71 | = | 595 | − | t | × | 47 | + | t | × | 40 |
| 68 | t | − | 4828 | − | 47 | t | + | 3337 | = | 595 | − | t | × | 47 | + | t | × | 40 |
| 21 | t | − | 1491 | = | 595 | − | 7 | t |
| 21 | t | + | 7 | t | = | 595 | + | 1491 |
| 28 | t | = | 595 | + | 1491 |
| 28 | t | = | 2086 |
| t | = | 2086 | ÷ | 28 |
| = | 2086 | × | 1 28 |
| = | 149 | × | 1 2 |
| t | = | 149 2 |
| t | = | 74.5 |