| 300 | x | − | 40 | x | − | ( | 280 | + | 120 | x | ) | = | 100 |
| Left side of the equation = | 260 | x | − | ( | 280 | + | 120 | x | ) |
| 260 | x | − | ( | 280 | + | 120 | x | ) | = | 100 |
| Left side of the equation = | 260 | x | − | 280 | − | 120 | x |
| = | 140 | x | − | 280 |
| 140 | x | − | 280 | = | 100 |
| 140 | x | = | 100 | + | 280 |
| 140 | x | = | 380 |
| x | = | 380 | ÷ | 140 |
| = | 380 | × | 1 140 |
| = | 19 | × | 1 7 |
| x | = | 19 7 |
| x | = | 2.714286 |