How many gold medals did Brazil win with a total of more than 55 medals?
CREATE TABLE "medal_table_by_country" (
  "rank" real,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("gold") FROM "medal_table_by_country" WHERE "nation"='brazil' AND "total">55;