Answer:
1. use the formula
[tex](n-2)180[/tex]
[tex](20 - 2)180\\18 * 180 = 3240[/tex]
2. use the formula
[tex]360/n\\360/12\\n = 30[/tex]
3. There is only one at 360 degrees
4. there are 6 rotational symmetries and the number of reflectional symmetries would be 6 as you can see:
