| 90 | − | x | = | 1 | ÷ | 3 | × | ( | 180 | − | x | ) | + | 12 |
| Right side of the equation = | 1 3 | ( | 180 | − | x | ) | + | 12 |
| 90 | − | x | = | 1 3 | ( | 180 | − | x | ) | + | 12 |
| Right side of the equation = | 1 3 | × | 180 | − | 1 3 | x | + | 12 |
| = | 60 | − | 1 3 | x | + | 12 |
| = | 72 | − | 1 3 | x |
| 90 | − | x | = | 72 | − | 1 3 | x |
| - | x | + | 1 3 | x | = | 72 | − | 90 |
| - | 2 3 | x | = | 72 | − | 90 |
| - | 2 3 | x | = | - | 18 |
| 18 | = | 2 3 | x |
2 3 | x | = | 18 |
| x | = | 18 | ÷ | 2 3 |
| = | 18 | × | 3 2 |
| = | 9 | × | 3 |
| x | = | 27 |