| 100 | ÷ | ( | 30 | + | x | ) | = | 60 | ÷ | ( | 20 | − | x | ) |
| 方程两边同时乘以: | ( | 30 | + | x | ) | , | ( | 20 | − | x | ) |
| 100 | ( | 20 | − | x | ) | = | 60 | ( | 30 | + | x | ) |
| 100 | × | 20 | − | 100 | x | = | 60 | ( | 30 | + | x | ) |
| 100 | × | 20 | − | 100 | x | = | 60 | × | 30 | + | 60 | x |
| 2000 | − | 100 | x | = | 1800 | + | 60 | x |
| - | 100 | x | − | 60 | x | = | 1800 | − | 2000 |
| - | 160 | x | = | 1800 | − | 2000 |
| - | 160 | x | = | - | 200 |
| 200 | = | 160 | x |
| 160 | x | = | 200 |
| x | = | 200 | ÷ | 160 |
| = | 200 | × | 1 160 |
| = | 5 | × | 1 4 |
| x | = | 5 4 |
| x | = | 1.25 |