| 21 | ÷ | x | − | 4 | = | 22 | ÷ | x | + | 4 | × | 3 2 |
| 方程两边同时乘以: | x |
| 21 | − | 4 | x | = | 22 | ÷ | 1 | × | 1 | + | 4 | × | 3 2 | x |
| - | 4 | x | − | 4 | × | 3 2 | x | = | 22 | ÷ | 1 | × | 1 | − | 21 |
| - | 4 | x | − | 6 | x | = | 22 | ÷ | 1 | × | 1 | − | 21 |
| - | 4 | x | − | 6 | x | = | 22 | − | 21 |
| - | 10 | x | = | 22 | − | 21 |
| - | 10 | x | = | 1 |
| - | 1 | = | 10 | x |
| 10 | x | = | - | 1 |
| x | = | - | 1 | ÷ | 10 |
| = | - | 1 | × | 1 10 |
| x | = | - | 1 10 |
| x | = | - 0.1 |