| 300 | x | = | 1200 | ( | x | + | 150 | ) |
| Right side of the equation = | 1200 | x | + | 1200 | × | 150 |
| = | 1200 | x | + | 180000 |
| 300 | x | = | 1200 | x | + | 180000 |
| 300 | x | − | 1200 | x | = | 180000 |
| - | 900 | x | = | 180000 |
| - | 180000 | = | 900 | x |
| 900 | x | = | - | 180000 |
| x | = | - | 180000 | ÷ | 900 |
| = | - | 180000 | × | 1 900 |
| = | - | 200 | × | 1 |
| x | = | - | 200 |