| 800 | = | 400 | ÷ | ( | 1 | + | x | ) | + | 300 | ÷ | ( | 1 | + | x | ) |
| 方程两边同时乘以: | ( | 1 | + | x | ) |
| 800 | ( | 1 | + | x | ) | = | 400 | + | 300 |
| 800 | × | 1 | + | 800 | x | = | 400 | + | 300 |
| 800 | + | 800 | x | = | 400 | + | 300 |
| 800 | + | 800 | x | = | 700 |
| 800 | x | = | 700 | − | 800 |
| 800 | x | = | - | 100 |
| x | = | - | 100 | ÷ | 800 |
| = | - | 100 | × | 1 800 |
| = | - | 1 | × | 1 8 |
| x | = | - | 1 8 |
| x | = | - 0.125 |