| 3200 | + | ( | 60 | − | x | ) | × | 100 | + | 90 | x | = | 9000 |
| Left side of the equation = | 3200 | + | 60 | × | 100 | − | x | × | 100 | + | 90 | x |
| = | 3200 | + | 6000 | − | x | × | 100 | + | 90 | x |
| = | 9200 | − | 10 | x |
| 9200 | − | 10 | x | = | 9000 |
| - | 10 | x | = | 9000 | − | 9200 |
| - | 10 | x | = | - | 200 |
| 200 | = | 10 | x |
| 10 | x | = | 200 |
| x | = | 200 | ÷ | 10 |
| = | 200 | × | 1 10 |
| = | 20 | × | 1 |
| x | = | 20 |