| ( | x | − | 20 | ) | ÷ | 3 | + | ( | x | − | 18 | ) | ÷ | 5 | + | ( | x | − | 16 | ) | ÷ | 7 | + | ( | x | − | 14 | ) | ÷ | 9 | = | 4 |
| 方程左边 = | x | × | 1 3 | − | 20 | × | 1 3 | + | ( | x | − | 18 | ) | × | 1 5 | + | ( | x | − | 16 | ) | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | x | × | 1 3 | − | 20 3 | + | ( | x | − | 18 | ) | × | 1 5 | + | ( | x | − | 16 | ) | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 1 3 | x | − | 20 3 | + | x | × | 1 5 | − | 18 | × | 1 5 | + | ( | x | − | 16 | ) | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 1 3 | x | − | 20 3 | + | x | × | 1 5 | − | 18 5 | + | ( | x | − | 16 | ) | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 8 15 | x | − | 154 15 | + | ( | x | − | 16 | ) | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 8 15 | x | − | 154 15 | + | x | × | 1 7 | − | 16 | × | 1 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 8 15 | x | − | 154 15 | + | x | × | 1 7 | − | 16 7 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 71 105 | x | − | 1318 105 | + | ( | x | − | 14 | ) | × | 1 9 |
| = | 71 105 | x | − | 1318 105 | + | x | × | 1 9 | − | 14 | × | 1 9 |
| = | 71 105 | x | − | 1318 105 | + | x | × | 1 9 | − | 14 9 |
| = | 248 315 | x | − | 4444 315 |
248 315 | x | − | 4444 315 | = | 4 |
248 315 | x | = | 4 | + | 4444 315 |
248 315 | x | = | 5704 315 |
| x | = | 5704 315 | ÷ | 248 315 |
| = | 5704 315 | × | 315 248 |
| = | 23 | × | 1 |
| x | = | 23 |