| 12 | x | + | 3 | ( | x | + | 3 | ) | + | 2 | ( | x | − | 1 | ) | = | 7 | x | + | 12 |
| Left side of the equation = | 12 | x | + | 3 | x | + | 3 | × | 3 | + | 2 | ( | x | − | 1 | ) |
| = | 12 | x | + | 3 | x | + | 9 | + | 2 | ( | x | − | 1 | ) |
| = | 15 | x | + | 9 | + | 2 | ( | x | − | 1 | ) |
| = | 15 | x | + | 9 | + | 2 | x | − | 2 | × | 1 |
| = | 15 | x | + | 9 | + | 2 | x | − | 2 |
| = | 17 | x | + | 7 |
| 17 | x | + | 7 | = | 7 | x | + | 12 |
| 17 | x | − | 7 | x | = | 12 | − | 7 |
| 10 | x | = | 12 | − | 7 |
| 10 | x | = | 5 |
| x | = | 5 | ÷ | 10 |
| = | 5 | × | 1 10 |
| = | 1 | × | 1 2 |
| x | = | 1 2 |
| x | = | 0.5 |