| ( | ( | 220 | + | 220 | + | 260 | ) | × | 21 | − | x | ) | × | 17 20 | = | ( | 220 | + | 220 | + | 260 | ) | × | 21 | × | 17 20 |
| 方程左边 = | ( | 220 | + | 220 | + | 260 | ) | × | 21 | × | 17 20 | − | x | × | 17 20 |
| = | ( | 220 | + | 220 | + | 260 | ) | × | 357 20 | − | x | × | 17 20 |
| = | 220 | × | 357 20 | + | 220 | × | 357 20 | + | 260 | × | 357 20 | − | 17 20 | x |
| = | 3927 | + | 3927 | + | 4641 | − | 17 20 | x |
| = | 12495 | − | 17 20 | x |
| 12495 | − | 17 20 | x | = | ( | 220 | + | 220 | + | 260 | ) | × | 21 | × | 17 20 |
| 方程右边 = | ( | 220 | + | 220 | + | 260 | ) | × | 357 20 |
| 12495 | − | 17 20 | x | = | ( | 220 | + | 220 | + | 260 | ) | × | 357 20 |
| 方程右边 = | 220 | × | 357 20 | + | 220 | × | 357 20 | + | 260 | × | 357 20 |
| = | 3927 | + | 3927 | + | 4641 |
| = | 12495 |
| 12495 | − | 17 20 | x | = | 12495 |
| - | 17 20 | x | = | 12495 | − | 12495 |
| - | 17 20 | x | = | 0 |
| - | 0 | = | 17 20 | x |
17 20 | x | = | - | 0 |
| x | = | - | 0 | ÷ | 17 20 |
| = | - | 0 | × | 20 17 |
| x | = | 0 |