| 50 | x | + | 100 | ( | 100 | − | x | ) | = | 8000 |
| Left side of the equation = | 50 | x | + | 100 | × | 100 | − | 100 | x |
| = | 50 | x | + | 10000 | − | 100 | x |
| = | - | 50 | x | + | 10000 |
| - | 50 | x | + | 10000 | = | 8000 |
| - | 50 | x | = | 8000 | − | 10000 |
| - | 50 | x | = | - | 2000 |
| 2000 | = | 50 | x |
| 50 | x | = | 2000 |
| x | = | 2000 | ÷ | 50 |
| = | 2000 | × | 1 50 |
| = | 40 | × | 1 |
| x | = | 40 |