CREATE TABLE table_name_21 (losses INTEGER, points VARCHAR(255), goals_against VARCHAR(255), goal_difference VARCHAR(255))
How many losses when goals against are more than 17, goal difference is more than 2 and points are more than 5?
    
SQL: SELECT AVG(losses) FROM table_name_21 WHERE goals_against > 17 AND goal_difference < 2 AND points > 5