What is the average crowd size when the home team scores 16.9 (105)?
CREATE TABLE "round_17" (
  "home_team" text,
  "home_team_score" text,
  "away_team" text,
  "away_team_score" text,
  "venue" text,
  "crowd" real,
  "date" text
);
SELECT AVG("crowd") FROM "round_17" WHERE "home_team_score"='16.9 (105)';