| ( | 30 | + | x | ) | ÷ | ( | 25 | − | x | ) | = | 9 | ÷ | 5 |
| 方程两边同时乘以: | ( | 25 | − | x | ) |
| ( | 30 | + | x | ) | = | 9 | ÷ | 5 | × | ( | 25 | − | x | ) |
| 30 | + | x | = | 9 | ÷ | 5 | × | ( | 25 | − | x | ) |
| 30 | + | x | = | 9 | ÷ | 5 | × | 25 | − | 9 | ÷ | 5 | × | x |
| 30 | + | x | = | 45 | − | 9 5 | x |
| x | + | 9 5 | x | = | 45 | − | 30 |
14 5 | x | = | 45 | − | 30 |
14 5 | x | = | 15 |
| x | = | 15 | ÷ | 14 5 |
| = | 15 | × | 5 14 |
| x | = | 75 14 |
| x | = | 5.357143 |