| x | + | 1 2 | ( | 180 | + | x | ) | = | 3 | ( | 90 | − | ( | 180 | − | x | ) | ) |
| 方程左边 = | x | + | 1 2 | × | 180 | + | 1 2 | x |
| = | x | + | 90 | + | 1 2 | x |
| = | 3 2 | x | + | 90 |
3 2 | x | + | 90 | = | 3 | ( | 90 | − | ( | 180 | − | x | ) | ) |
| 方程右边 = | 3 | × | 90 | − | 3 | ( | 180 | − | x | ) |
| = | 270 | − | 3 | ( | 180 | − | x | ) |
| = | 270 | − | 3 | × | 180 | + | 3 | x |
| = | 270 | − | 540 | + | 3 | x |
| = | - | 270 | + | 3 | x |
3 2 | x | + | 90 | = | - | 270 | + | 3 | x |
3 2 | x | − | 3 | x | = | - | 270 | − | 90 |
| - | 3 2 | x | = | - | 270 | − | 90 |
| - | 3 2 | x | = | - | 360 |
| 360 | = | 3 2 | x |
3 2 | x | = | 360 |
| x | = | 360 | ÷ | 3 2 |
| = | 360 | × | 2 3 |
| = | 120 | × | 2 |
| x | = | 240 |