| ( | 25 | − | 25 | ) | ÷ | ( | 25 | − | 21 | ) | = | ( | 55 | − | t | ) | ÷ | ( | t | − | 41 | ) |
| 方程两边同时乘以: | ( | 25 | − | 21 | ) | , | ( | t | − | 41 | ) |
| ( | 25 | − | 25 | ) | ( | t | − | 41 | ) | = | ( | 55 | − | t | ) | ( | 25 | − | 21 | ) |
| 25 | ( | t | − | 41 | ) | − | 25 | ( | t | − | 41 | ) | = | ( | 55 | − | t | ) | ( | 25 | − | 21 | ) |
| 25 | ( | t | − | 41 | ) | − | 25 | ( | t | − | 41 | ) | = | 55 | ( | 25 | − | 21 | ) | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 25 | × | 41 | − | 25 | ( | t | − | 41 | ) | = | 55 | ( | 25 | − | 21 | ) | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 25 | × | 41 | − | 25 | ( | t | − | 41 | ) | = | 55 | × | 25 | − | 55 | × | 21 | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 1025 | − | 25 | ( | t | − | 41 | ) | = | 1375 | − | 1155 | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 1025 | − | 25 | ( | t | − | 41 | ) | = | 220 | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 1025 | − | 25 | t | + | 25 | × | 41 | = | 220 | − | t | ( | 25 | − | 21 | ) |
| 25 | t | − | 1025 | − | 25 | t | + | 25 | × | 41 | = | 220 | − | t | × | 25 | + | t | × | 21 |
| 25 | t | − | 1025 | − | 25 | t | + | 1025 | = | 220 | − | t | × | 25 | + | t | × | 21 |
| 0 | t | − | 0 | = | 220 | − | 4 | t |
| 4 | t | = | 220 | + | 0 |
| 4 | t | = | 220 |
| t | = | 220 | ÷ | 4 |
| = | 220 | × | 1 4 |
| = | 55 | × | 1 |
| t | = | 55 |