| ( | 1000 | − | 100 | x | ) | ( | 8 | + | 2 | x | ) | = | 10000 |
| 方程左边 = | 1000 | ( | 8 | + | 2 | x | ) | − | 100 | x | ( | 8 | + | 2 | x | ) |
| = | 1000 | × | 8 | + | 1000 | × | 2 | x | − | 100 | x | ( | 8 | + | 2 | x | ) |
| = | 8000 | + | 2000 | x | − | 100 | x | ( | 8 | + | 2 | x | ) |
| = | 8000 | + | 2000 | x | − | 100 | x | × | 8 | − | 100 | x | × | 2 | x |
| = | 8000 | + | 2000 | x | − | 800 | x | − | 200 | x | x |
| = | 8000 | + | 1200 | x | − | 200 | x | x |
| 8000 | + | 1200 | x | − | 200 | x | x | = | 10000 |