| ( | 1 | − | 2 | ÷ | 3 | ) | X | = | ( | 1 | − | 4 | ÷ | 5 | ) | ( | 800 | − | X | ) |
| 方程左边 = | 1 | X | − | 2 | ÷ | 3 | × | X |
| = | 1 | X | − | 2 3 | X |
| = | 1 3 | X |
1 3 | X | = | ( | 1 | − | 4 | ÷ | 5 | ) | ( | 800 | − | X | ) |
| 方程右边 = | 1 | ( | 800 | − | X | ) | − | 4 | ÷ | 5 | × | ( | 800 | − | X | ) |
| = | 1 | ( | 800 | − | X | ) | − | 4 5 | ( | 800 | − | X | ) |
| = | 1 | × | 800 | − | 1 | X | − | 4 5 | ( | 800 | − | X | ) |
| = | 800 | − | 1 | X | − | 4 5 | ( | 800 | − | X | ) |
| = | 800 | − | 1 | X | − | 4 5 | × | 800 | + | 4 5 | X |
| = | 800 | − | 1 | X | − | 640 | + | 4 5 | X |
| = | 160 | − | 1 5 | X |
1 3 | X | = | 160 | − | 1 5 | X |
1 3 | X | + | 1 5 | X | = | 160 |
8 15 | X | = | 160 |
| X | = | 160 | ÷ | 8 15 |
| = | 160 | × | 15 8 |
| = | 20 | × | 15 |
| X | = | 300 |