| 10 | ( | 200 | + | 100 | a | ) | − | a | ( | 200 | + | 100 | a | ) | − | 150 | a | = | 1800 |
| 方程左边 = | 10 | × | 200 | + | 10 | × | 100 | a | − | a | ( | 200 | + | 100 | a | ) | − | 150 | a |
| = | 2000 | + | 1000 | a | − | a | ( | 200 | + | 100 | a | ) | − | 150 | a |
| = | 2000 | + | 850 | a | − | a | ( | 200 | + | 100 | a | ) |
| = | 2000 | + | 850 | a | − | a | × | 200 | − | a | × | 100 | a |
| = | 2000 | + | 650 | a | − | a | × | 100 | a |
| 2000 | + | 650 | a | − | a | × | 100 | a | = | 1800 |