| ( | 2 | a | − | 240 | ) | ÷ | ( | a | − | 480 | ) | + | 5 | = | ( | a | − | 240 | ) | ÷ | 480 |
| 方程两边同时乘以: | ( | a | − | 480 | ) |
| ( | 2 | a | − | 240 | ) | + | 5 | ( | a | − | 480 | ) | = | ( | a | − | 240 | ) | ÷ | 480 | × | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | ( | a | − | 480 | ) | = | ( | a | − | 240 | ) | ÷ | 480 | × | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | ( | a | − | 480 | ) | = | a | ÷ | 480 | × | ( | a | − | 480 | ) | − | 240 | ÷ | 480 | × | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | ( | a | − | 480 | ) | = | a | × | 1 480 | ( | a | − | 480 | ) | − | 1 2 | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | a | − | 5 | × | 480 | = | a | × | 1 480 | ( | a | − | 480 | ) | − | 1 2 | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | a | − | 5 | × | 480 | = | a | × | 1 480 | a | − | a | × | 1 480 | × | 480 | − | 1 2 | ( | a | − | 480 | ) |
| 2 | a | − | 240 | + | 5 | a | − | 2400 | = | a | × | 1 480 | a | − | a | × | 1 | − | 1 2 | ( | a | − | 480 | ) |
| 7 | a | − | 2640 | = | a | × | 1 480 | a | − | 1 | a | − | 1 2 | ( | a | − | 480 | ) |
| 7 | a | − | 2640 | = | a | × | 1 480 | a | − | 1 | a | − | 1 2 | a | + | 1 2 | × | 480 |
| 7 | a | − | 2640 | = | a | × | 1 480 | a | − | 1 | a | − | 1 2 | a | + | 240 |
| 7 | a | − | 2640 | = | a | × | 1 480 | a | − | 3 2 | a | + | 240 |