| ( | x | − | 20 | ) | ( | 500 | + | 2 | x | ) | = | 10000 |
| Left side of the equation = | x | ( | 500 | + | 2 | x | ) | − | 20 | ( | 500 | + | 2 | x | ) |
| = | x | × | 500 | + | x | × | 2 | x | − | 20 | ( | 500 | + | 2 | x | ) |
| = | 500 | x | + | x | × | 2 | x | − | 20 | × | 500 | − | 20 | × | 2 | x |
| = | 500 | x | + | x | × | 2 | x | − | 10000 | − | 40 | x |
| = | 460 | x | + | x | × | 2 | x | − | 10000 |
| 460 | x | + | x | × | 2 | x | − | 10000 | = | 10000 |