| ( | 1000 | − | 10 | x | ) | ( | x | − | 30 | ) | = | 10000 |
| Left side of the equation = | 1000 | ( | x | − | 30 | ) | − | 10 | x | ( | x | − | 30 | ) |
| = | 1000 | x | − | 1000 | × | 30 | − | 10 | x | ( | x | − | 30 | ) |
| = | 1000 | x | − | 30000 | − | 10 | x | ( | x | − | 30 | ) |
| = | 1000 | x | − | 30000 | − | 10 | x | x | + | 10 | x | × | 30 |
| = | 1000 | x | − | 30000 | − | 10 | x | x | + | 300 | x |
| = | 1300 | x | − | 30000 | − | 10 | x | x |
| 1300 | x | − | 30000 | − | 10 | x | x | = | 10000 |