| ( | X | + | 40 | ) | × | 8 100 | − | X | = | 12 |
| Left side of the equation = | X | × | 8 100 | + | 40 | × | 8 100 | − | X |
| = | X | × | 8 100 | + | 16 5 | − | X |
| = | - | 23 25 | X | + | 16 5 |
| - | 23 25 | X | + | 16 5 | = | 12 |
| - | 23 25 | X | = | 12 | − | 16 5 |
| - | 23 25 | X | = | 44 5 |
| - | 44 5 | = | 23 25 | X |
23 25 | X | = | - | 44 5 |
| X | = | - | 44 5 | ÷ | 23 25 |
| = | - | 44 5 | × | 25 23 |
| = | - | 44 | × | 5 23 |
| X | = | - | 220 23 |
| X | = | - 9.565217 |