| ( | x | − | 40 | ) | ( | 50000 | − | 500 | x | ) | = | 350000 |
| Left side of the equation = | x | ( | 50000 | − | 500 | x | ) | − | 40 | ( | 50000 | − | 500 | x | ) |
| = | x | × | 50000 | − | x | × | 500 | x | − | 40 | ( | 50000 | − | 500 | x | ) |
| = | 50000 | x | − | x | × | 500 | x | − | 40 | × | 50000 | + | 40 | × | 500 | x |
| = | 50000 | x | − | x | × | 500 | x | − | 2000000 | + | 20000 | x |
| = | 70000 | x | − | x | × | 500 | x | − | 2000000 |
| 70000 | x | − | x | × | 500 | x | − | 2000000 | = | 350000 |