| 345 | + | 20 100 | ( | x | − | 3500 | − | 4500 | ) | = | 445 |
| 方程左边 = | 345 | + | 20 100 | x | − | 20 100 | × | 3500 | − | 20 100 | × | 4500 |
| = | 345 | + | 20 100 | x | − | 700 | − | 900 |
| = | - | 1255 | + | 20 100 | x |
| - | 1255 | + | 20 100 | x | = | 445 |
20 100 | x | = | 445 | + | 1255 |
20 100 | x | = | 1700 |
| x | = | 1700 | ÷ | 20 100 |
| = | 1700 | × | 100 20 |
| = | 85 | × | 100 |
| x | = | 8500 |