| ( | n | − | 2 | ) | × | 180 | ÷ | n | × | 2 | ÷ | 3 | = | 180 | − | ( | n | − | 2 | ) | × | 180 | ÷ | n |
| Multiply both sides of the equation by: | n |
| ( | n | − | 2 | ) | × | 180 | × | 2 | ÷ | 3 | = | 180 | n | − | ( | n | − | 2 | ) | × | 180 | ÷ | 1 | × | 1 |
| n | × | 180 | × | 2 | ÷ | 3 | − | 2 | × | 180 | × | 2 | ÷ | 3 | = | 180 | n | − | ( | n | − | 2 | ) | × | 180 | ÷ | 1 | × | 1 |
| n | × | 180 | × | 2 | ÷ | 3 | − | 2 | × | 180 | × | 2 | ÷ | 3 | = | 180 | n | − | n | × | 180 | ÷ | 1 | × | 1 | + | 2 | × | 180 | ÷ | 1 | × | 1 |
| n | × | 120 | − | 240 | = | 180 | n | − | n | × | 180 | + | 360 |
| 120 | n | − | 240 | = | 0 | n | + | 360 |
| 120 | n | = | 360 | + | 240 |
| 120 | n | = | 600 |
| n | = | 600 | ÷ | 120 |
| = | 600 | × | 1 120 |
| = | 5 | × | 1 |
| n | = | 5 |