| 50 | x | + | 80 | ( | 500 | − | x | ) | = | 28000 |
| Left side of the equation = | 50 | x | + | 80 | × | 500 | − | 80 | x |
| = | 50 | x | + | 40000 | − | 80 | x |
| = | - | 30 | x | + | 40000 |
| - | 30 | x | + | 40000 | = | 28000 |
| - | 30 | x | = | 28000 | − | 40000 |
| - | 30 | x | = | - | 12000 |
| 12000 | = | 30 | x |
| 30 | x | = | 12000 |
| x | = | 12000 | ÷ | 30 |
| = | 12000 | × | 1 30 |
| = | 400 | × | 1 |
| x | = | 400 |