Table: blue_jays_1991_games
Columns: date
opponent
score
loss
attendance
record

Question: On what date was the opponent the White Sox and the record 18-13?
SQL: SELECT "date" FROM blue_jays_1991_games WHERE "opponent" = 'white sox' AND "record" = '18-13'

Question: What was the average attendance when the record was 19-13?
SQL: SELECT AVG("attendance") FROM blue_jays_1991_games WHERE "record" = '19-13'