| ( | 399 10 | ( | 1 | + | 20 100 | ) | ) | + | ( | 3 100 | x | ) | = | x |
| 方程左边 = | 399 10 | ( | 1 | + | 20 100 | ) | + | ( | 3 100 | x | ) |
| = | 399 10 | × | 1 | + | 399 10 | × | 20 100 | + | ( | 3 100 | x | ) |
| = | 399 10 | + | 399 50 | + | ( | 3 100 | x | ) |
| = | 1197 25 | + | ( | 3 100 | x | ) |
| = | 1197 25 | + | 3 100 | x |
1197 25 | + | 3 100 | x | = | x |
3 100 | x | − | x | = | - | 1197 25 |
| - | 97 100 | x | = | - | 1197 25 |
1197 25 | = | 97 100 | x |
97 100 | x | = | 1197 25 |
| x | = | 1197 25 | ÷ | 97 100 |
| = | 1197 25 | × | 100 97 |
| = | 1197 | × | 4 97 |
| x | = | 4788 97 |
| x | = | 49.360825 |