In which ward of more than 55,000 inhabitants are there more crimes of intimidation with extortion?
more than 55000 inhabitants refers to Population > 55000; 'INTIMIDATION' is the primary_description; 'EXTORTION' refers to secondary_description; more crime refers to Count(ward_no)
SELECT T3.ward_no FROM IUCR AS T1 INNER JOIN Crime AS T2 ON T2.iucr_no = T1.iucr_no INNER JOIN Ward AS T3 ON T3.ward_no = T2.ward_no WHERE T1.primary_description = 'INTIMIDATION' AND T1.secondary_description = 'EXTORTION' AND T3.Population > 55000 GROUP BY T3.ward_no ORDER BY COUNT(T3.ward_no) DESC LIMIT 1