| ( | 3 | ( | - | ( | 21 | ÷ | 17 | ) | ) | − | 1 | ) | ( | 3 | ÷ | 5 | ) | = | x |
| 方程左边 = | 3 | ( | - | ( | 21 | ÷ | 17 | ) | ) | ( | 3 | ÷ | 5 | ) | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 3 | ( | 21 | ÷ | 17 | ) | ( | 3 | ÷ | 5 | ) | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 3 | × | 21 | ÷ | 17 | × | ( | 3 | ÷ | 5 | ) | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 63 17 | ( | 3 | ÷ | 5 | ) | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 63 17 | × | 3 | ÷ | 5 | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 189 85 | − | 1 | ( | 3 | ÷ | 5 | ) |
| = | - | 189 85 | − | 1 | × | 3 | ÷ | 5 |
| = | - | 189 85 | − | 3 5 |
| = | - | 48 17 |
| - | 48 17 | = | x |
| - | x | = | 48 17 |
| - | 48 17 | = | x |
| x | = | - | 48 17 |