| 24 | ÷ | ( | 300 | + | x | ) | = | 15 | ÷ | ( | 120 | + | x | ) |
| 方程两边同时乘以: | ( | 300 | + | x | ) | , | ( | 120 | + | x | ) |
| 24 | ( | 120 | + | x | ) | = | 15 | ( | 300 | + | x | ) |
| 24 | × | 120 | + | 24 | x | = | 15 | ( | 300 | + | x | ) |
| 24 | × | 120 | + | 24 | x | = | 15 | × | 300 | + | 15 | x |
| 2880 | + | 24 | x | = | 4500 | + | 15 | x |
| 24 | x | − | 15 | x | = | 4500 | − | 2880 |
| 9 | x | = | 4500 | − | 2880 |
| 9 | x | = | 1620 |
| x | = | 1620 | ÷ | 9 |
| = | 1620 | × | 1 9 |
| = | 180 | × | 1 |
| x | = | 180 |