| ( | 5 | ( | 640 | + | X | ) | + | 60 | + | 48 | + | 8 | + | 24 | ) | ÷ | ( | 640 | + | 15 | + | 16 | + | 4 | + | 24 | + | X | ) | = | 49 10 |
| 方程两边同时乘以: | ( | 640 | + | 15 | + | 16 | + | 4 | + | 24 | + | X | ) |
| ( | 5 | ( | 640 | + | X | ) | + | 60 | + | 48 | + | 8 | + | 24 | ) | = | 49 10 | ( | 640 | + | 15 | + | 16 | + | 4 | + | 24 | + | X | ) |
| 5 | ( | 640 | + | X | ) | + | 60 | + | 48 | + | 8 | + | 24 | = | 49 10 | ( | 640 | + | 15 | + | 16 | + | 4 | + | 24 | + | X | ) |
| 5 | ( | 640 | + | X | ) | + | 60 | + | 48 | + | 8 | + | 24 | = | 49 10 | × | 640 | + | 49 10 | × | 15 | + | 49 10 | × | 16 | + | 49 10 | × | 4 | + | 49 10 | × | 24 | + | 49 10 | X |
| 5 | ( | 640 | + | X | ) | + | 60 | + | 48 | + | 8 | + | 24 | = | 3136 | + | 147 2 | + | 392 5 | + | 98 5 | + | 588 5 | + | 49 10 | X |
| 5 | ( | 640 | + | X | ) | + | 140 | = | 34251 10 | + | 49 10 | X |
| 5 | × | 640 | + | 5 | X | + | 140 | = | 34251 10 | + | 49 10 | X |
| 3200 | + | 5 | X | + | 140 | = | 34251 10 | + | 49 10 | X |
| 3340 | + | 5 | X | = | 34251 10 | + | 49 10 | X |
| 5 | X | − | 49 10 | X | = | 34251 10 | − | 3340 |
1 10 | X | = | 34251 10 | − | 3340 |
1 10 | X | = | 851 10 |
| X | = | 851 10 | ÷ | 1 10 |
| = | 851 10 | × | 10 |
| = | 851 | × | 1 |
| X | = | 851 |