| 120 | ÷ | ( | x | − | 120 | ) | = | ( | x | + | 2 | ÷ | 7 | × | x | ) | ÷ | ( | 2 | x | − | 2 | ÷ | 7 | × | x | ) |
| 方程两边同时乘以: | ( | x | − | 120 | ) | , | ( | 2 | x | − | 2 | ÷ | 7 | × | x | ) |
| 120 | ( | 2 | x | − | 2 | ÷ | 7 | × | x | ) | = | ( | x | + | 2 | ÷ | 7 | × | x | ) | ( | x | − | 120 | ) |
| 120 | × | 2 | x | − | 120 | × | 2 | ÷ | 7 | × | x | = | ( | x | + | 2 | ÷ | 7 | × | x | ) | ( | x | − | 120 | ) |
| 120 | × | 2 | x | − | 120 | × | 2 | ÷ | 7 | × | x | = | x | ( | x | − | 120 | ) | + | 2 | ÷ | 7 | × | x | ( | x | − | 120 | ) |
| 240 | x | − | 240 7 | x | = | x | ( | x | − | 120 | ) | + | 2 7 | x | ( | x | − | 120 | ) |
1440 7 | x | = | x | ( | x | − | 120 | ) | + | 2 7 | x | ( | x | − | 120 | ) |
1440 7 | x | = | x | x | − | x | × | 120 | + | 2 7 | x | ( | x | − | 120 | ) |
1440 7 | x | = | x | x | − | 120 | x | + | 2 7 | x | x | − | 2 7 | x | × | 120 |
1440 7 | x | = | x | x | − | 120 | x | + | 2 7 | x | x | − | 240 7 | x |
1440 7 | x | = | x | x | − | 1080 7 | x | + | 2 7 | x | x |