| 3 | ( | x | − | 600 | ) | = | 4 | ( | x | − | 1200 | ) |
| Left side of the equation = | 3 | x | − | 3 | × | 600 |
| = | 3 | x | − | 1800 |
| 3 | x | − | 1800 | = | 4 | ( | x | − | 1200 | ) |
| Right side of the equation = | 4 | x | − | 4 | × | 1200 |
| = | 4 | x | − | 4800 |
| 3 | x | − | 1800 | = | 4 | x | − | 4800 |
| 3 | x | − | 4 | x | = | - | 4800 | + | 1800 |
| - | x | = | - | 4800 | + | 1800 |
| - | x | = | - | 4800 | + | 1800 |
| - | x | = | - | 3000 |
| 3000 | = | x |
| x | = | 3000 |