| ( | 77 | + | X | ) | ÷ | ( | 116 | + | X | ) | = | 90 100 |
| 方程两边同时乘以: | ( | 116 | + | X | ) |
| ( | 77 | + | X | ) | = | 90 100 | ( | 116 | + | X | ) |
| 77 | + | X | = | 90 100 | ( | 116 | + | X | ) |
| 77 | + | X | = | 90 100 | × | 116 | + | 90 100 | X |
| 77 | + | X | = | 522 5 | + | 90 100 | X |
| X | − | 90 100 | X | = | 522 5 | − | 77 |
1 10 | X | = | 522 5 | − | 77 |
1 10 | X | = | 137 5 |
| X | = | 137 5 | ÷ | 1 10 |
| = | 137 5 | × | 10 |
| = | 137 | × | 2 |
| X | = | 274 |