| 30 | ( | x | − | 15 | ) | = | 18 | ( | x | + | 15 | ) |
| Left side of the equation = | 30 | x | − | 30 | × | 15 |
| = | 30 | x | − | 450 |
| 30 | x | − | 450 | = | 18 | ( | x | + | 15 | ) |
| Right side of the equation = | 18 | x | + | 18 | × | 15 |
| = | 18 | x | + | 270 |
| 30 | x | − | 450 | = | 18 | x | + | 270 |
| 30 | x | − | 18 | x | = | 270 | + | 450 |
| 12 | x | = | 270 | + | 450 |
| 12 | x | = | 720 |
| x | = | 720 | ÷ | 12 |
| = | 720 | × | 1 12 |
| = | 60 | × | 1 |
| x | = | 60 |