| ( | 180 | − | x | ) | + | ( | 180 | − | 2 | x | ) | + | x | = | 180 |
| Left side of the equation = | 180 | − | x | + | ( | 180 | − | 2 | x | ) | + | x |
| = | 180 | − | 0 | x | + | ( | 180 | − | 2 | x | ) |
| = | 180 | − | 0 | x | + | 180 | − | 2 | x |
| = | 360 | − | 2 | x |
| 360 | − | 2 | x | = | 180 |
| - | 2 | x | = | 180 | − | 360 |
| - | 2 | x | = | - | 180 |
| 180 | = | 2 | x |
| 2 | x | = | 180 |
| x | = | 180 | ÷ | 2 |
| = | 180 | × | 1 2 |
| = | 90 | × | 1 |
| x | = | 90 |