I don't know if it's supposed to do with (n-2)180
Also please explain :D

Step-by-step explanation:
[tex] sum \: of \: interior \\ \: angels \: is \: 2340 \: degrees. \\
(n−2)⋅180=2340 \\
180n - 360=2340 \\ 180n = 2700 \\
n=15 \\
number \: of \: sides=15[/tex]
the polygon is 15 sided.