| ( | 10 | − | X | ) | × | 800 | − | 1000 | = | 3000 |
| Left side of the equation = | 10 | × | 800 | − | X | × | 800 | − | 1000 |
| = | 8000 | − | X | × | 800 | − | 1000 |
| = | 7000 | − | 800 | X |
| 7000 | − | 800 | X | = | 3000 |
| - | 800 | X | = | 3000 | − | 7000 |
| - | 800 | X | = | - | 4000 |
| 4000 | = | 800 | X |
| 800 | X | = | 4000 |
| X | = | 4000 | ÷ | 800 |
| = | 4000 | × | 1 800 |
| = | 5 | × | 1 |
| X | = | 5 |