| 12 | ÷ | 1 | × | x | + | 9 | ÷ | 1 | × | ( | 10 | − | x | ) | = | 1 |
| Left side of the equation = | 12 | x | + | 9 | ( | 10 | − | x | ) |
| 12 | x | + | 9 | ( | 10 | − | x | ) | = | 1 |
| Left side of the equation = | 12 | x | + | 9 | × | 10 | − | 9 | x |
| = | 12 | x | + | 90 | − | 9 | x |
| = | 3 | x | + | 90 |
| 3 | x | + | 90 | = | 1 |
| 3 | x | = | 1 | − | 90 |
| 3 | x | = | - | 89 |
| x | = | - | 89 | ÷ | 3 |
| = | - | 89 | × | 1 3 |
| x | = | - | 89 3 |
| x | = | - 29.666667 |