| 81 | X | − | ( | 1000 | − | X | ) | × | 210 | = | - | 5000 |
| Left side of the equation = | 81 | X | − | 1000 | × | 210 | + | X | × | 210 |
| = | 81 | X | − | 210000 | + | X | × | 210 |
| = | 291 | X | − | 210000 |
| 291 | X | − | 210000 | = | - | 5000 |
| 291 | X | = | - | 5000 | + | 210000 |
| 291 | X | = | 205000 |
| X | = | 205000 | ÷ | 291 |
| = | 205000 | × | 1 291 |
| X | = | 205000 291 |
| X | = | 704.467354 |