| ( | 421 | + | x | ) | ÷ | ( | 478 | + | x | ) | = | 9 10 |
| 方程两边同时乘以: | ( | 478 | + | x | ) |
| ( | 421 | + | x | ) | = | 9 10 | ( | 478 | + | x | ) |
| 421 | + | x | = | 9 10 | ( | 478 | + | x | ) |
| 421 | + | x | = | 9 10 | × | 478 | + | 9 10 | x |
| 421 | + | x | = | 2151 5 | + | 9 10 | x |
| x | − | 9 10 | x | = | 2151 5 | − | 421 |
1 10 | x | = | 2151 5 | − | 421 |
1 10 | x | = | 46 5 |
| x | = | 46 5 | ÷ | 1 10 |
| = | 46 5 | × | 10 |
| = | 46 | × | 2 |
| x | = | 92 |