| 9 | ( | 1 | ÷ | 30 | + | 1 | ÷ | 20 | ) | + | ( | x | − | 9 | ) | ÷ | 20 | = | 1 |
| 方程左边 = | 9 | × | 1 | ÷ | 30 | + | 9 | × | 1 | ÷ | 20 | + | ( | x | − | 9 | ) | × | 1 20 |
| = | 3 10 | + | 9 20 | + | ( | x | − | 9 | ) | × | 1 20 |
| = | 3 4 | + | ( | x | − | 9 | ) | × | 1 20 |
| = | 3 4 | + | x | × | 1 20 | − | 9 | × | 1 20 |
| = | 3 4 | + | x | × | 1 20 | − | 9 20 |
| = | 3 10 | + | 1 20 | x |
3 10 | + | 1 20 | x | = | 1 |
1 20 | x | = | 1 | − | 3 10 |
1 20 | x | = | 7 10 |
| x | = | 7 10 | ÷ | 1 20 |
| = | 7 10 | × | 20 |
| = | 7 | × | 2 |
| x | = | 14 |