| 80 | x | + | 210 | ( | 1 | − | x | ) | = | 130 |
| Left side of the equation = | 80 | x | + | 210 | × | 1 | − | 210 | x |
| = | 80 | x | + | 210 | − | 210 | x |
| = | - | 130 | x | + | 210 |
| - | 130 | x | + | 210 | = | 130 |
| - | 130 | x | = | 130 | − | 210 |
| - | 130 | x | = | - | 80 |
| 80 | = | 130 | x |
| 130 | x | = | 80 |
| x | = | 80 | ÷ | 130 |
| = | 80 | × | 1 130 |
| = | 8 | × | 1 13 |
| x | = | 8 13 |
| x | = | 0.615385 |