| 3 | ( | x | − | 15 | ) | + | 5 | ( | x | − | 1 | ) | − | 4 | = | - | 6 |
| Left side of the equation = | 3 | x | − | 3 | × | 15 | + | 5 | ( | x | − | 1 | ) | − | 4 |
| = | 3 | x | − | 45 | + | 5 | ( | x | − | 1 | ) | − | 4 |
| = | 3 | x | − | 49 | + | 5 | ( | x | − | 1 | ) |
| = | 3 | x | − | 49 | + | 5 | x | − | 5 | × | 1 |
| = | 3 | x | − | 49 | + | 5 | x | − | 5 |
| = | 8 | x | − | 54 |
| 8 | x | − | 54 | = | - | 6 |
| 8 | x | = | - | 6 | + | 54 |
| 8 | x | = | 48 |
| x | = | 48 | ÷ | 8 |
| = | 48 | × | 1 8 |
| = | 6 | × | 1 |
| x | = | 6 |