| ( | 8400 | + | 40 | + | X | ) | × | 4 125 | = | 4 | X |
| 方程左边 = | 8400 | × | 4 125 | + | 40 | × | 4 125 | + | X | × | 4 125 |
| = | 1344 5 | + | 32 25 | + | X | × | 4 125 |
| = | 6752 25 | + | 4 125 | X |
6752 25 | + | 4 125 | X | = | 4 | X |
4 125 | X | − | 4 | X | = | - | 6752 25 |
| - | 496 125 | X | = | - | 6752 25 |
6752 25 | = | 496 125 | X |
496 125 | X | = | 6752 25 |
| X | = | 6752 25 | ÷ | 496 125 |
| = | 6752 25 | × | 125 496 |
| = | 422 | × | 5 31 |
| X | = | 2110 31 |
| X | = | 68.064516 |