| ( | 19 | − | 17 | ) | ÷ | ( | 17 | − | 8 | ) | = | ( | 40 | − | t | ) | ÷ | ( | t | − | 30 | ) |
| 方程两边同时乘以: | ( | 17 | − | 8 | ) | , | ( | t | − | 30 | ) |
| ( | 19 | − | 17 | ) | ( | t | − | 30 | ) | = | ( | 40 | − | t | ) | ( | 17 | − | 8 | ) |
| 19 | ( | t | − | 30 | ) | − | 17 | ( | t | − | 30 | ) | = | ( | 40 | − | t | ) | ( | 17 | − | 8 | ) |
| 19 | ( | t | − | 30 | ) | − | 17 | ( | t | − | 30 | ) | = | 40 | ( | 17 | − | 8 | ) | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 19 | × | 30 | − | 17 | ( | t | − | 30 | ) | = | 40 | ( | 17 | − | 8 | ) | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 19 | × | 30 | − | 17 | ( | t | − | 30 | ) | = | 40 | × | 17 | − | 40 | × | 8 | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 570 | − | 17 | ( | t | − | 30 | ) | = | 680 | − | 320 | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 570 | − | 17 | ( | t | − | 30 | ) | = | 360 | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 570 | − | 17 | t | + | 17 | × | 30 | = | 360 | − | t | ( | 17 | − | 8 | ) |
| 19 | t | − | 570 | − | 17 | t | + | 17 | × | 30 | = | 360 | − | t | × | 17 | + | t | × | 8 |
| 19 | t | − | 570 | − | 17 | t | + | 510 | = | 360 | − | t | × | 17 | + | t | × | 8 |
| 2 | t | − | 60 | = | 360 | − | 9 | t |
| 2 | t | + | 9 | t | = | 360 | + | 60 |
| 11 | t | = | 360 | + | 60 |
| 11 | t | = | 420 |
| t | = | 420 | ÷ | 11 |
| = | 420 | × | 1 11 |
| t | = | 420 11 |
| t | = | 38.181818 |