| 360 | × | 2 | = | ( | n | − | 2 | ) | × | 180 |
| Left side of the equation = | 720 |
| 720 | = | ( | n | − | 2 | ) | × | 180 |
| Right side of the equation = | n | × | 180 | − | 2 | × | 180 |
| = | n | × | 180 | − | 360 |
| 720 | = | 180 | n | − | 360 |
| - | 180 | n | = | - | 360 | − | 720 |
| - | 180 | n | = | - | 1080 |
| 1080 | = | 180 | n |
| 180 | n | = | 1080 |
| n | = | 1080 | ÷ | 180 |
| = | 1080 | × | 1 180 |
| = | 6 | × | 1 |
| n | = | 6 |