Compute the average score of the university located in Brazil.
average score refers to avg(score); located in Brazil refers to country_name = 'Brazil';
SELECT AVG(T2.score) FROM university AS T1 INNER JOIN university_ranking_year AS T2 ON T1.id = T2.university_id INNER JOIN country AS T3 ON T3.id = T1.country_id WHERE T3.country_name = 'Brazil'