| ( | 210 | + | x | ) | ÷ | ( | 257 | + | x | ) | = | 91 100 |
| 方程两边同时乘以: | ( | 257 | + | x | ) |
| ( | 210 | + | x | ) | = | 91 100 | ( | 257 | + | x | ) |
| 210 | + | x | = | 91 100 | ( | 257 | + | x | ) |
| 210 | + | x | = | 91 100 | × | 257 | + | 91 100 | x |
| 210 | + | x | = | 23387 100 | + | 91 100 | x |
| x | − | 91 100 | x | = | 23387 100 | − | 210 |
9 100 | x | = | 23387 100 | − | 210 |
9 100 | x | = | 2387 100 |
| x | = | 2387 100 | ÷ | 9 100 |
| = | 2387 100 | × | 100 9 |
| = | 2387 | × | 1 9 |
| x | = | 2387 9 |
| x | = | 265.222222 |