On average, how many community areas are there in a side?
average = Divide(Count(ward_no), Count(side))
SELECT CAST(COUNT(T1.ward_no) AS REAL) / COUNT(DISTINCT T3.side) FROM Ward AS T1 INNER JOIN Crime AS T2 ON T2.ward_no = T1.ward_no INNER JOIN Community_Area AS T3 ON T3.community_area_no = T2.community_area_no