| 30000000 | = | x | × | 3 50 | ÷ | ( | 1 200000000 | ( | 1 | + | x | ) | ÷ | x | ) |
| 方程两边同时乘以: | ( | 1 200000000 | ( | 1 | + | x | ) | ÷ | x | ) |
| 30000000 | ( | 1 200000000 | ( | 1 | + | x | ) | ÷ | x | ) | = | x | × | 3 50 |
| 30000000 | × | 1 200000000 | ( | 1 | + | x | ) | ÷ | x | = | x | × | 3 50 |
3 20 | ( | 1 | + | x | ) | ÷ | x | = | x | × | 3 50 |
| 方程两边同时乘以: | x |
3 20 | ( | 1 | + | x | ) | = | 3 50 | x | x |
3 20 | × | 1 | + | 3 20 | x | = | 3 50 | x | x |
3 20 | + | 3 20 | x | = | 3 50 | x | x |