49 20 | × | 342 | ( | 20 | + | X | ) | = | 42 25 | × | 690 | ( | 20 | − | X | ) |
| 方程左边 = | 8379 10 | ( | 20 | + | X | ) |
8379 10 | ( | 20 | + | X | ) | = | 42 25 | × | 690 | ( | 20 | − | X | ) |
| 方程左边 = | 8379 10 | × | 20 | + | 8379 10 | X |
| = | 16758 | + | 8379 10 | X |
| 16758 | + | 8379 10 | X | = | 42 25 | × | 690 | ( | 20 | − | X | ) |
| 方程右边 = | 5796 5 | ( | 20 | − | X | ) |
| 16758 | + | 8379 10 | X | = | 5796 5 | ( | 20 | − | X | ) |
| 方程右边 = | 5796 5 | × | 20 | − | 5796 5 | X |
| = | 23184 | − | 5796 5 | X |
| 16758 | + | 8379 10 | X | = | 23184 | − | 5796 5 | X |
8379 10 | X | + | 5796 5 | X | = | 23184 | − | 16758 |
19971 10 | X | = | 23184 | − | 16758 |
19971 10 | X | = | 6426 |
| X | = | 6426 | ÷ | 19971 10 |
| = | 6426 | × | 10 19971 |
| = | 102 | × | 10 317 |
| X | = | 1020 317 |
| X | = | 3.217666 |