| ( | 475 | + | x | ) | ÷ | ( | 390 | + | x | ) | = | 13 10 |
| 方程两边同时乘以: | ( | 390 | + | x | ) |
| ( | 475 | + | x | ) | = | 13 10 | ( | 390 | + | x | ) |
| 475 | + | x | = | 13 10 | ( | 390 | + | x | ) |
| 475 | + | x | = | 13 10 | × | 390 | + | 13 10 | x |
| 475 | + | x | = | 507 | + | 13 10 | x |
| x | − | 13 10 | x | = | 507 | − | 475 |
| - | 3 10 | x | = | 507 | − | 475 |
| - | 3 10 | x | = | 32 |
| - | 32 | = | 3 10 | x |
3 10 | x | = | - | 32 |
| x | = | - | 32 | ÷ | 3 10 |
| = | - | 32 | × | 10 3 |
| x | = | - | 320 3 |
| x | = | - 106.666667 |