| ( | 1702 | + | x | ) | ÷ | ( | 1940 | + | x | ) | = | 9 10 |
| 方程两边同时乘以: | ( | 1940 | + | x | ) |
| ( | 1702 | + | x | ) | = | 9 10 | ( | 1940 | + | x | ) |
| 1702 | + | x | = | 9 10 | ( | 1940 | + | x | ) |
| 1702 | + | x | = | 9 10 | × | 1940 | + | 9 10 | x |
| 1702 | + | x | = | 1746 | + | 9 10 | x |
| x | − | 9 10 | x | = | 1746 | − | 1702 |
1 10 | x | = | 1746 | − | 1702 |
1 10 | x | = | 44 |
| x | = | 44 | ÷ | 1 10 |
| = | 44 | × | 10 |
| x | = | 440 |