| ( | 50 | × | 10 | + | 70 | x | ) | ÷ | ( | 10 | + | x | ) | = | 55 |
| 方程两边同时乘以: | ( | 10 | + | x | ) |
| ( | 50 | × | 10 | + | 70 | x | ) | = | 55 | ( | 10 | + | x | ) |
| 50 | × | 10 | + | 70 | x | = | 55 | ( | 10 | + | x | ) |
| 50 | × | 10 | + | 70 | x | = | 55 | × | 10 | + | 55 | x |
| 500 | + | 70 | x | = | 550 | + | 55 | x |
| 70 | x | − | 55 | x | = | 550 | − | 500 |
| 15 | x | = | 550 | − | 500 |
| 15 | x | = | 50 |
| x | = | 50 | ÷ | 15 |
| = | 50 | × | 1 15 |
| = | 10 | × | 1 3 |
| x | = | 10 3 |
| x | = | 3.333333 |