What is the average number of incidents per month in 2018 in the ward with the most population?
in 2018 refers to date like '%2018%'; ward with most population refers to Max(Population); average number of incident per month refers to Divide(Count(ward_no), 12)
SELECT COUNT(T1.ward_no) / 12 AS average FROM Ward AS T1 INNER JOIN Crime AS T2 ON T1.ward_no = T2.ward_no WHERE T2.date LIKE '%2018%' AND T1.Population = ( SELECT MAX(T1.Population) FROM Ward AS T1 INNER JOIN Crime AS T2 ON T1.ward_no = T2.ward_no WHERE T2.date LIKE '%2018%' )