What is the average attendance when Brewers are the opponent with a score of 6–3?
CREATE TABLE "game_log" (
  "date" text,
  "opponent" text,
  "score" text,
  "loss" text,
  "attendance" real,
  "record" text
);
SELECT AVG("attendance") FROM "game_log" WHERE "opponent"='brewers' AND "score"='6–3';