| ( | 1000 | − | 140 | ) | × | 10 | + | ( | 1000 | − | 220 | ) | ( | x | − | 10 | ) | = | 800 | x |
| 方程左边 = | 1000 | × | 10 | − | 140 | × | 10 | + | ( | 1000 | − | 220 | ) | ( | x | − | 10 | ) |
| = | 10000 | − | 1400 | + | ( | 1000 | − | 220 | ) | ( | x | − | 10 | ) |
| = | 8600 | + | ( | 1000 | − | 220 | ) | ( | x | − | 10 | ) |
| = | 8600 | + | 1000 | ( | x | − | 10 | ) | − | 220 | ( | x | − | 10 | ) |
| = | 8600 | + | 1000 | x | − | 1000 | × | 10 | − | 220 | ( | x | − | 10 | ) |
| = | 8600 | + | 1000 | x | − | 10000 | − | 220 | ( | x | − | 10 | ) |
| = | - | 1400 | + | 1000 | x | − | 220 | ( | x | − | 10 | ) |
| = | - | 1400 | + | 1000 | x | − | 220 | x | + | 220 | × | 10 |
| = | - | 1400 | + | 1000 | x | − | 220 | x | + | 2200 |
| = | 800 | + | 780 | x |
| 800 | + | 780 | x | = | 800 | x |
| 780 | x | − | 800 | x | = | - | 800 |
| - | 20 | x | = | - | 800 |
| 800 | = | 20 | x |
| 20 | x | = | 800 |
| x | = | 800 | ÷ | 20 |
| = | 800 | × | 1 20 |
| = | 40 | × | 1 |
| x | = | 40 |