| ( | 12 | + | 2 | x | ) | ( | 800 | − | 10 | x | ) | − | ( | 7200 | + | 1000 | x | ) | = | 4960 |
| 方程左边 = | 12 | ( | 800 | − | 10 | x | ) | + | 2 | x | ( | 800 | − | 10 | x | ) | − | ( | 7200 | + | 1000 | x | ) |
| = | 12 | × | 800 | − | 12 | × | 10 | x | + | 2 | x | ( | 800 | − | 10 | x | ) | − | ( | 7200 | + | 1000 | x | ) |
| = | 9600 | − | 120 | x | + | 2 | x | ( | 800 | − | 10 | x | ) | − | ( | 7200 | + | 1000 | x | ) |
| = | 9600 | − | 120 | x | + | 2 | x | × | 800 | − | 2 | x | × | 10 | x | − | ( | 7200 | + | 1000 | x | ) |
| = | 9600 | − | 120 | x | + | 1600 | x | − | 20 | x | x | − | ( | 7200 | + | 1000 | x | ) |
| = | 9600 | + | 1480 | x | − | 20 | x | x | − | ( | 7200 | + | 1000 | x | ) |
| = | 9600 | + | 1480 | x | − | 20 | x | x | − | 7200 | − | 1000 | x |
| = | 2400 | + | 480 | x | − | 20 | x | x |
| 2400 | + | 480 | x | − | 20 | x | x | = | 4960 |