Hmm, can you tell me the addresses that have the highest average monthly rental?
SELECT T2.address_id FROM Student_Addresses AS T1 JOIN Students AS T2 ON T1.student_id   =   T2.student_id GROUP BY T1.student_id ORDER BY AVG ( monthly_rental )  DESC LIMIT 1
highest average monthly rental refers to MAX(AVG(monthly_rental)); addresses that have refers to address_id;