| ( | x | − | 30 | ) | ( | 150 | − | 3 | x | ) | = | 0 |
| Left side of the equation = | x | ( | 150 | − | 3 | x | ) | − | 30 | ( | 150 | − | 3 | x | ) |
| = | x | × | 150 | − | x | × | 3 | x | − | 30 | ( | 150 | − | 3 | x | ) |
| = | 150 | x | − | x | × | 3 | x | − | 30 | × | 150 | + | 30 | × | 3 | x |
| = | 150 | x | − | x | × | 3 | x | − | 4500 | + | 90 | x |
| = | 240 | x | − | x | × | 3 | x | − | 4500 |
| 240 | x | − | x | × | 3 | x | − | 4500 | = | 0 |