select u.university,qd.difficult_level, round(count(qpd.device_id)/(count(distinct qpd.device_id)),4) as avg_answer_cnt from (user_profile u inner join question_practice_detail qpd on u.device_id = qpd.device_id) inner join question_detail qd on qpd.question_id = qd.question_id group by u.univers...