| ( | 9 20 | + | x | ) | ÷ | ( | 1 | + | x | ) | = | 2 5 |
| 方程两边同时乘以: | ( | 1 | + | x | ) |
| ( | 9 20 | + | x | ) | = | 2 5 | ( | 1 | + | x | ) |
9 20 | + | x | = | 2 5 | ( | 1 | + | x | ) |
9 20 | + | x | = | 2 5 | × | 1 | + | 2 5 | x |
9 20 | + | x | = | 2 5 | + | 2 5 | x |
| x | − | 2 5 | x | = | 2 5 | − | 9 20 |
3 5 | x | = | 2 5 | − | 9 20 |
3 5 | x | = | - | 1 20 |
| x | = | - | 1 20 | ÷ | 3 5 |
| = | - | 1 20 | × | 5 3 |
| = | - | 1 4 | × | 1 3 |
| x | = | - | 1 12 |
| x | = | - 0.083333 |