| 200 | x | + | 800 | − | 12 | x | = | 9 | x | + | 36 | − | 131 |
| Left side of the equation = | 188 | x | + | 800 |
| 188 | x | + | 800 | = | 9 | x | + | 36 | − | 131 |
| Right side of the equation = | 9 | x | − | 95 |
| 188 | x | + | 800 | = | 9 | x | − | 95 |
| 188 | x | − | 9 | x | = | - | 95 | − | 800 |
| 179 | x | = | - | 95 | − | 800 |
| 179 | x | = | - | 895 |
| x | = | - | 895 | ÷ | 179 |
| = | - | 895 | × | 1 179 |
| x | = | - | 895 179 |
| x | = | - | 5 |