| ( | ( | X | + | 1 | ) | ÷ | 2 | ) | − | ( | ( | X | + | 3 | ) | ÷ | 5 | ) | = | 4 5 |
| 方程左边 = | ( | X | + | 1 | ) | ÷ | 2 | − | ( | ( | X | + | 3 | ) | ÷ | 5 | ) |
| = | X | × | 1 2 | + | 1 | × | 1 2 | − | ( | ( | X | + | 3 | ) | ÷ | 5 | ) |
| = | X | × | 1 2 | + | 1 2 | − | ( | ( | X | + | 3 | ) | ÷ | 5 | ) |
| = | 1 2 | X | + | 1 2 | − | ( | X | + | 3 | ) | ÷ | 5 |
| = | 1 2 | X | + | 1 2 | − | X | × | 1 5 | − | 3 | × | 1 5 |
| = | 1 2 | X | + | 1 2 | − | X | × | 1 5 | − | 3 5 |
| = | 3 10 | X | − | 1 10 |
3 10 | X | − | 1 10 | = | 4 5 |
3 10 | X | = | 4 5 | + | 1 10 |
3 10 | X | = | 9 10 |
| X | = | 9 10 | ÷ | 3 10 |
| = | 9 10 | × | 10 3 |
| = | 3 | × | 1 |
| X | = | 3 |