| ( | 1800 | + | x | ) | ÷ | ( | 5700 | + | x | ) | = | 1 | ÷ | 2 |
| 方程两边同时乘以: | ( | 5700 | + | x | ) |
| ( | 1800 | + | x | ) | = | 1 | ÷ | 2 | × | ( | 5700 | + | x | ) |
| 1800 | + | x | = | 1 | ÷ | 2 | × | ( | 5700 | + | x | ) |
| 1800 | + | x | = | 1 | ÷ | 2 | × | 5700 | + | 1 | ÷ | 2 | × | x |
| 1800 | + | x | = | 2850 | + | 1 2 | x |
| x | − | 1 2 | x | = | 2850 | − | 1800 |
1 2 | x | = | 2850 | − | 1800 |
1 2 | x | = | 1050 |
| x | = | 1050 | ÷ | 1 2 |
| = | 1050 | × | 2 |
| x | = | 2100 |