How many 24 years old competitors competed in Men's Basketball?
24 years old competitors refer to id where age = 24; Men's Basketball refers to event_name = 'Basketball Men''s Basketball';
SELECT COUNT(T2.person_id) FROM competitor_event AS T1 INNER JOIN games_competitor AS T2 ON T1.competitor_id = T2.id INNER JOIN event AS T3 ON T1.event_id = T3.id WHERE T3.event_name LIKE 'Basketball Men%s Basketball' AND T2.age = 24