| 4000 | ÷ | X | × | 7 5 | = | 8400 | ÷ | X | + | 10 |
| Multiply both sides of the equation by: | X |
| 4000 | × | 7 5 | = | 8400 | ÷ | 1 | × | 1 | + | 10 | X |
| - | 10 | X | = | 8400 | ÷ | 1 | × | 1 | − | 4000 | × | 7 5 |
| - | 10 | X | = | 8400 | − | 5600 |
| - | 10 | X | = | 2800 |
| - | 2800 | = | 10 | X |
| 10 | X | = | - | 2800 |
| X | = | - | 2800 | ÷ | 10 |
| = | - | 2800 | × | 1 10 |
| = | - | 280 | × | 1 |
| X | = | - | 280 |