| ( | 3 | x | − | 180 | ) | ÷ | ( | 4 | x | − | 180 | ) | = | 9 | ÷ | 13 |
| 方程两边同时乘以: | ( | 4 | x | − | 180 | ) |
| ( | 3 | x | − | 180 | ) | = | 9 | ÷ | 13 | × | ( | 4 | x | − | 180 | ) |
| 3 | x | − | 180 | = | 9 | ÷ | 13 | × | ( | 4 | x | − | 180 | ) |
| 3 | x | − | 180 | = | 9 | ÷ | 13 | × | 4 | x | − | 9 | ÷ | 13 | × | 180 |
| 3 | x | − | 180 | = | 36 13 | x | − | 1620 13 |
| 3 | x | − | 36 13 | x | = | - | 1620 13 | + | 180 |
3 13 | x | = | - | 1620 13 | + | 180 |
3 13 | x | = | 720 13 |
| x | = | 720 13 | ÷ | 3 13 |
| = | 720 13 | × | 13 3 |
| = | 240 | × | 1 |
| x | = | 240 |