| 2100 | + | 2500 | ( | 50 | − | x | ) | = | 90000 |
| Left side of the equation = | 2100 | + | 2500 | × | 50 | − | 2500 | x |
| = | 2100 | + | 125000 | − | 2500 | x |
| = | 127100 | − | 2500 | x |
| 127100 | − | 2500 | x | = | 90000 |
| - | 2500 | x | = | 90000 | − | 127100 |
| - | 2500 | x | = | - | 37100 |
| 37100 | = | 2500 | x |
| 2500 | x | = | 37100 |
| x | = | 37100 | ÷ | 2500 |
| = | 37100 | × | 1 2500 |
| = | 371 | × | 1 25 |
| x | = | 371 25 |
| x | = | 14.84 |