| 40 | ( | 1 | + | x | ) | + | 50 | ( | 1 | − | 2 | x | ) | = | 8320 |
| Left side of the equation = | 40 | × | 1 | + | 40 | x | + | 50 | ( | 1 | − | 2 | x | ) |
| = | 40 | + | 40 | x | + | 50 | ( | 1 | − | 2 | x | ) |
| = | 40 | + | 40 | x | + | 50 | × | 1 | − | 50 | × | 2 | x |
| = | 40 | + | 40 | x | + | 50 | − | 100 | x |
| = | 90 | − | 60 | x |
| 90 | − | 60 | x | = | 8320 |
| - | 60 | x | = | 8320 | − | 90 |
| - | 60 | x | = | 8230 |
| - | 8230 | = | 60 | x |
| 60 | x | = | - | 8230 |
| x | = | - | 8230 | ÷ | 60 |
| = | - | 8230 | × | 1 60 |
| = | - | 823 | × | 1 6 |
| x | = | - | 823 6 |
| x | = | - 137.166667 |