| 6 | ( | 3 | x | − | 1 | ) | = | 21 | − | 4 | ( | 3 | − | 4 | x | ) |
| Left side of the equation = | 6 | × | 3 | x | − | 6 | × | 1 |
| = | 18 | x | − | 6 |
| 18 | x | − | 6 | = | 21 | − | 4 | ( | 3 | − | 4 | x | ) |
| Right side of the equation = | 21 | − | 4 | × | 3 | + | 4 | × | 4 | x |
| = | 21 | − | 12 | + | 16 | x |
| = | 9 | + | 16 | x |
| 18 | x | − | 6 | = | 9 | + | 16 | x |
| 18 | x | − | 16 | x | = | 9 | + | 6 |
| 2 | x | = | 9 | + | 6 |
| 2 | x | = | 15 |
| x | = | 15 | ÷ | 2 |
| = | 15 | × | 1 2 |
| x | = | 15 2 |
| x | = | 7.5 |