| 40 | x | + | 80 | x | − | 480 | = | 120 |
| Left side of the equation = | 120 | x | − | 480 |
| 120 | x | − | 480 | = | 120 |
| 120 | x | = | 120 | + | 480 |
| 120 | x | = | 600 |
| x | = | 600 | ÷ | 120 |
| = | 600 | × | 1 120 |
| = | 5 | × | 1 |
| x | = | 5 |
| - | 80 | x | + | 480 | − | 40 | x | = | 120 |
| Left side of the equation = | - | 120 | x | + | 480 |
| - | 120 | x | + | 480 | = | 120 |
| - | 120 | x | = | 120 | − | 480 |
| - | 120 | x | = | - | 360 |
| 360 | = | 120 | x |
| 120 | x | = | 360 |
| x | = | 360 | ÷ | 120 |
| = | 360 | × | 1 120 |
| = | 3 | × | 1 |
| x | = | 3 |