| ( | 199 | + | X | ) | ÷ | ( | 222 | + | X | ) | = | 19 20 |
| 方程两边同时乘以: | ( | 222 | + | X | ) |
| ( | 199 | + | X | ) | = | 19 20 | ( | 222 | + | X | ) |
| 199 | + | X | = | 19 20 | ( | 222 | + | X | ) |
| 199 | + | X | = | 19 20 | × | 222 | + | 19 20 | X |
| 199 | + | X | = | 2109 10 | + | 19 20 | X |
| X | − | 19 20 | X | = | 2109 10 | − | 199 |
1 20 | X | = | 2109 10 | − | 199 |
1 20 | X | = | 119 10 |
| X | = | 119 10 | ÷ | 1 20 |
| = | 119 10 | × | 20 |
| = | 119 | × | 2 |
| X | = | 238 |