| ( | x | − | 200 | ) | × | 4 5 | + | 200 | = | ( | x | − | 100 | ) | × | 9 10 | + | 100 |
| 方程左边 = | x | × | 4 5 | − | 200 | × | 4 5 | + | 200 |
| = | x | × | 4 5 | − | 160 | + | 200 |
| = | 4 5 | x | + | 40 |
4 5 | x | + | 40 | = | ( | x | − | 100 | ) | × | 9 10 | + | 100 |
| 方程右边 = | x | × | 9 10 | − | 100 | × | 9 10 | + | 100 |
| = | x | × | 9 10 | − | 90 | + | 100 |
| = | 9 10 | x | + | 10 |
4 5 | x | + | 40 | = | 9 10 | x | + | 10 |
4 5 | x | − | 9 10 | x | = | 10 | − | 40 |
| - | 1 10 | x | = | 10 | − | 40 |
| - | 1 10 | x | = | - | 30 |
| 30 | = | 1 10 | x |
1 10 | x | = | 30 |
| x | = | 30 | ÷ | 1 10 |
| = | 30 | × | 10 |
| x | = | 300 |