| ( | 400 | x | − | 6000 | ) | ÷ | ( | 400 | x | ) | = | 7 20 |
| 方程两边同时乘以: | ( | 400 | x | ) |
| ( | 400 | x | − | 6000 | ) | = | 7 20 | ( | 400 | x | ) |
| 400 | x | − | 6000 | = | 7 20 | ( | 400 | x | ) |
| 400 | x | − | 6000 | = | 7 20 | × | 400 | x |
| 400 | x | − | 6000 | = | 140 | x |
| 400 | x | − | 140 | x | = | 6000 |
| 260 | x | = | 6000 |
| x | = | 6000 | ÷ | 260 |
| = | 6000 | × | 1 260 |
| = | 300 | × | 1 13 |
| x | = | 300 13 |
| x | = | 23.076923 |