how many sides has a polygon if the sum of its angle is 3240

Hello :)

The sum of the angles of a polygon is (n-2)*180°.
If your sum is 3240°, you have to solve this equation :
[tex](n-2)*180 = 3240[/tex]
[tex]n-2 = 18[/tex]
[tex]n = 20[/tex]

So your polygon is 20-sided :)

Good evening !