| ( | X | − | 1 | ) | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | ÷ | 1 2 | × | X | × | 1 2 | = | 275 |
| 方程左边 = | ( | X | − | 1 | ) | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| ( | X | − | 1 | ) | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X | = | 275 |
| 方程左边 = | X | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | 1 | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| = | X | × | 30 | − | X | ( | X | − | 10 | ) | ÷ | 1 2 | − | 1 | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 30 | X | − | X | X | × | 2 | + | X | × | 10 | × | 2 | − | 1 | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 |
| = | 30 | X | − | X | X | × | 2 | + | X | × | 20 | − | 1 | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 50 | X | − | X | X | × | 2 | − | 1 | ( | 30 | − | ( | X | − | 10 | ) | ÷ | 1 2 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 50 | X | − | X | X | × | 2 | − | 1 | × | 30 | + | 1 | ( | X | − | 10 | ) | ÷ | 1 2 | − | ( | X | − | 10 | ) | × | 1 |
| = | 50 | X | − | X | X | × | 2 | − | 30 | + | 2 | ( | X | − | 10 | ) | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 50 | X | − | X | X | × | 2 | − | 30 | + | 2 | X | − | 2 | × | 10 | − | ( | X | − | 10 | ) | × | 1 |
| = | 50 | X | − | X | X | × | 2 | − | 30 | + | 2 | X | − | 20 | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 52 | X | − | X | X | × | 2 | − | 50 | − | ( | X | − | 10 | ) | × | 1 | X |
| = | 52 | X | − | X | X | × | 2 | − | 50 | − | X | × | 1 | X | + | 10 | × | 1 | X |
| = | 52 | X | − | X | X | × | 2 | − | 50 | − | X | × | 1 | X | + | 10 | X |
| = | 62 | X | − | X | X | × | 2 | − | 50 | − | X | × | 1 | X |
| 62 | X | − | X | X | × | 2 | − | 50 | − | X | × | 1 | X | = | 275 |