CREATE TABLE table_name_91 (attendance NUMBER, opponent VARCHAR2, round VARCHAR2)

Which Attendance has an Opponent of perth glory, and a Round of 9?
SELECT MIN(attendance) FROM table_name_91 WHERE opponent = "perth glory" AND round = "9"
SELECT MIN("attendance") FROM "table_name_91" WHERE "9" = "round" AND "opponent" = "perth glory"