| ( | x | + | 9 | ) | ÷ | ( | x | + | 4 | + | 9 | ) | = | 7 | ÷ | 9 |
| 方程两边同时乘以: | ( | x | + | 4 | + | 9 | ) |
| ( | x | + | 9 | ) | = | 7 | ÷ | 9 | × | ( | x | + | 4 | + | 9 | ) |
| x | + | 9 | = | 7 | ÷ | 9 | × | ( | x | + | 4 | + | 9 | ) |
| x | + | 9 | = | 7 | ÷ | 9 | × | x | + | 7 | ÷ | 9 | × | 4 | + | 7 | ÷ | 9 | × | 9 |
| x | + | 9 | = | 7 9 | x | + | 28 9 | + | 7 |
| x | + | 9 | = | 7 9 | x | + | 91 9 |
| x | − | 7 9 | x | = | 91 9 | − | 9 |
2 9 | x | = | 91 9 | − | 9 |
2 9 | x | = | 10 9 |
| x | = | 10 9 | ÷ | 2 9 |
| = | 10 9 | × | 9 2 |
| = | 5 | × | 1 |
| x | = | 5 |