| ( | 1 | + | 3 20 | × | 20 | x | ) | ( | 1 | + | x | ) | ÷ | 3 20 | = | 7 20 |
| 方程左边 = | 1 | ( | 1 | + | x | ) | × | 20 3 | + | 3 20 | × | 20 | x | ( | 1 | + | x | ) | × | 20 3 |
| = | 20 3 | ( | 1 | + | x | ) | + | 20 | x | ( | 1 | + | x | ) |
| = | 20 3 | × | 1 | + | 20 3 | x | + | 20 | x | ( | 1 | + | x | ) |
| = | 20 3 | + | 20 3 | x | + | 20 | x | ( | 1 | + | x | ) |
| = | 20 3 | + | 20 3 | x | + | 20 | x | × | 1 | + | 20 | x | x |
| = | 20 3 | + | 20 3 | x | + | 20 | x | + | 20 | x | x |
| = | 20 3 | + | 80 3 | x | + | 20 | x | x |
20 3 | + | 80 3 | x | + | 20 | x | x | = | 7 20 |