| ( | X | + | 21 20 | X | ) | ( | 1 | + | 9 100 | ) | = | 9000 |
| 方程左边 = | X | ( | 1 | + | 9 100 | ) | + | 21 20 | X | ( | 1 | + | 9 100 | ) |
| = | X | × | 1 | + | X | × | 9 100 | + | 21 20 | X | ( | 1 | + | 9 100 | ) |
| = | 109 100 | X | + | 21 20 | X | ( | 1 | + | 9 100 | ) |
| = | 109 100 | X | + | 21 20 | X | × | 1 | + | 21 20 | X | × | 9 100 |
| = | 109 100 | X | + | 21 20 | X | + | 189 2000 | X |
| = | 4469 2000 | X |
4469 2000 | X | = | 9000 |
| X | = | 9000 | ÷ | 4469 2000 |
| = | 9000 | × | 2000 4469 |
| X | = | 18000000 4469 |
| X | = | 4027.746699 |