| ( | 5 | + | 1 10 | x | ) | ÷ | ( | 100 | + | x | ) | = | 9 100 |
| 方程两边同时乘以: | ( | 100 | + | x | ) |
| ( | 5 | + | 1 10 | x | ) | = | 9 100 | ( | 100 | + | x | ) |
| 5 | + | 1 10 | x | = | 9 100 | ( | 100 | + | x | ) |
| 5 | + | 1 10 | x | = | 9 100 | × | 100 | + | 9 100 | x |
| 5 | + | 1 10 | x | = | 9 | + | 9 100 | x |
1 10 | x | − | 9 100 | x | = | 9 | − | 5 |
1 100 | x | = | 9 | − | 5 |
1 100 | x | = | 4 |
| x | = | 4 | ÷ | 1 100 |
| = | 4 | × | 100 |
| x | = | 400 |