| ( | 99 20 | − | x | ) | ÷ | 99 20 | = | 71 5000 |
| 方程左边 = | 99 20 | × | 20 99 | − | x | × | 20 99 |
| = | 1 | − | x | × | 20 99 |
| 1 | − | 20 99 | x | = | 71 5000 |
| - | 20 99 | x | = | 71 5000 | − | 1 |
| - | 20 99 | x | = | - | 4929 5000 |
4929 5000 | = | 20 99 | x |
20 99 | x | = | 4929 5000 |
| x | = | 4929 5000 | ÷ | 20 99 |
| = | 4929 5000 | × | 99 20 |
| x | = | 487971 100000 |
| x | = | 4.87971 |