the sum of the interior angles of a ngon is 180(n-2)
so
if we had
300=180(n-2)
divide boths ies by 180
5/3=n-2
add 2 to both sides (2=6/3)
11/3=n
you can't have 11/3 number of sides, yo have to have a whole number of sides
so no, that is impossible, will never happen