| 900000 | = | X | ( | 30 | − | 10 | ) | − | 200000 |
| Right side of the equation = | X | × | 30 | − | X | × | 10 | − | 200000 |
| = | 20 | X | − | 200000 |
| 900000 | = | 20 | X | − | 200000 |
| - | 20 | X | = | - | 200000 | − | 900000 |
| - | 20 | X | = | - | 1100000 |
| 1100000 | = | 20 | X |
| 20 | X | = | 1100000 |
| X | = | 1100000 | ÷ | 20 |
| = | 1100000 | × | 1 20 |
| = | 55000 | × | 1 |
| X | = | 55000 |