| 100 | ÷ | ( | 78 | + | 74 | + | X | ) | = | 11 20 |
| 方程两边同时乘以: | ( | 78 | + | 74 | + | X | ) |
| 100 | = | 11 20 | ( | 78 | + | 74 | + | X | ) |
| 100 | = | 11 20 | × | 78 | + | 11 20 | × | 74 | + | 11 20 | X |
| 100 | = | 429 10 | + | 407 10 | + | 11 20 | X |
| 100 | = | 418 5 | + | 11 20 | X |
| - | 11 20 | X | = | 418 5 | − | 100 |
| - | 11 20 | X | = | - | 82 5 |
82 5 | = | 11 20 | X |
11 20 | X | = | 82 5 |
| X | = | 82 5 | ÷ | 11 20 |
| = | 82 5 | × | 20 11 |
| = | 82 | × | 4 11 |
| X | = | 328 11 |
| X | = | 29.818182 |