Table: t_1931_vfl_games
Columns: home_team
home_team_score
away_team
away_team_score
venue
crowd
date

Question: On what date did Fitzroy have a home team score of 8.13 (61)?
SQL: SELECT "date" FROM t_1931_vfl_games WHERE "home_team_score" = '8.13 (61)'

Question: What is the average crowd for the home team of North Melbourne?
SQL: SELECT AVG("crowd") FROM t_1931_vfl_games WHERE "home_team" = 'north melbourne'