Database: university
Question: Among the universities in Australia, how many of them have more than 15000 students in 2011?
SQL: SELECT COUNT(*) FROM university AS T1 INNER JOIN university_year AS T2 ON T1.id = T2.university_id INNER JOIN country AS T3 ON T3.id = T1.country_id WHERE T3.country_name = 'Australia' AND T2.year = 2011 AND T2.num_students > 15000