| 300 | = | ( | - | 15 | − | x | ) | ( | 50 | − | 3 | x | ) |
| Right side of the equation = | - | 15 | ( | 50 | − | 3 | x | ) | − | x | ( | 50 | − | 3 | x | ) |
| = | - | 15 | × | 50 | + | 15 | × | 3 | x | − | x | ( | 50 | − | 3 | x | ) |
| = | - | 750 | + | 45 | x | − | x | ( | 50 | − | 3 | x | ) |
| = | - | 750 | + | 45 | x | − | x | × | 50 | + | x | × | 3 | x |
| = | - | 750 | − | 5 | x | + | x | × | 3 | x |
| 300 | = | - | 750 | − | 5 | x | + | x | × | 3 | x |