| x | − | ( | 1 | ÷ | 8 | × | x | + | 21 | ) | − | ( | 1 | − | 6 | x | − | 6 | ) | = | 172 |
| 方程左边 = | x | − | 1 | ÷ | 8 | × | x | − | 21 | − | ( | 1 | − | 6 | x | − | 6 | ) |
| = | x | − | 1 8 | x | − | 21 | − | ( | 1 | − | 6 | x | − | 6 | ) |
| = | 7 8 | x | − | 21 | − | ( | 1 | − | 6 | x | − | 6 | ) |
| = | 7 8 | x | − | 21 | − | 1 | + | 6 | x | + | 6 |
| = | 55 8 | x | − | 16 |
55 8 | x | − | 16 | = | 172 |
55 8 | x | = | 172 | + | 16 |
55 8 | x | = | 188 |
| x | = | 188 | ÷ | 55 8 |
| = | 188 | × | 8 55 |
| x | = | 1504 55 |
| x | = | 27.345455 |