| 3 | + | 20 | ( | 3 | ÷ | x | ) | + | 6 | = | 9 | + | 20 | ( | 9 | ÷ | x | ) |
| 3 | + | 20 | × | 3 | ÷ | x | + | 6 | = | 9 | + | 20 | ( | 9 | ÷ | x | ) |
| 3 | + | 20 | × | 3 | ÷ | x | + | 6 | = | 9 | + | 20 | × | 9 | ÷ | x |
| 3 | + | 60 | ÷ | x | + | 6 | = | 9 | + | 180 | ÷ | x |
| 9 | + | 60 | ÷ | x | = | 9 | + | 180 | ÷ | x |
| 方程两边同时乘以: | x |
| 9 | x | + | 60 | = | 9 | x | + | 180 | ÷ | 1 | × | 1 |
| 9 | x | − | 9 | x | = | 180 | ÷ | 1 | × | 1 | − | 60 |
| 9 | x | − | 9 | x | = | 180 | − | 60 |
| 0 | x | = | 180 | − | 60 |
| 0 | x | = | 120 |