| 1200 | = | ( | x | − | 3 | ) | ( | - | 2 | x | + | 160 | ) |
| Right side of the equation = | x | ( | - | 2 | x | + | 160 | ) | − | 3 | ( | - | 2 | x | + | 160 | ) |
| = | - | x | × | 2 | x | + | x | × | 160 | − | 3 | ( | - | 2 | x | + | 160 | ) |
| = | - | x | × | 2 | x | + | 160 | x | + | 3 | × | 2 | x | − | 3 | × | 160 |
| = | - | x | × | 2 | x | + | 160 | x | + | 6 | x | − | 480 |
| = | - | x | × | 2 | x | + | 166 | x | − | 480 |
| 1200 | = | - | x | × | 2 | x | + | 166 | x | − | 480 |