| ( | x | − | 30 | ) | ( | 100 | − | 2 | x | ) | = | 200 |
| Left side of the equation = | x | ( | 100 | − | 2 | x | ) | − | 30 | ( | 100 | − | 2 | x | ) |
| = | x | × | 100 | − | x | × | 2 | x | − | 30 | ( | 100 | − | 2 | x | ) |
| = | 100 | x | − | x | × | 2 | x | − | 30 | × | 100 | + | 30 | × | 2 | x |
| = | 100 | x | − | x | × | 2 | x | − | 3000 | + | 60 | x |
| = | 160 | x | − | x | × | 2 | x | − | 3000 |
| 160 | x | − | x | × | 2 | x | − | 3000 | = | 200 |