| ( | ( | X | × | 2 | + | 6 | ) | × | 2 | + | 6 | ) | × | 2 | + | 6 | = | 999 |
| 方程左边 = | ( | X | × | 2 | + | 6 | ) | × | 2 | × | 2 | + | 6 | × | 2 | + | 6 |
| = | ( | X | × | 2 | + | 6 | ) | × | 4 | + | 12 | + | 6 |
| = | ( | X | × | 2 | + | 6 | ) | × | 4 | + | 18 |
| = | X | × | 2 | × | 4 | + | 6 | × | 4 | + | 18 |
| = | X | × | 8 | + | 24 | + | 18 |
| = | 8 | X | + | 42 |
| 8 | X | + | 42 | = | 999 |
| 8 | X | = | 999 | − | 42 |
| 8 | X | = | 957 |
| X | = | 957 | ÷ | 8 |
| = | 957 | × | 1 8 |
| X | = | 957 8 |
| X | = | 119.625 |