CREATE TABLE table_77237 ("Opposing Team" TEXT, "Against" FLOAT, "Date" TEXT, "Venue" TEXT, "Status" TEXT)

What was the average of againsts on 21/5/1997?
SELECT AVG("Against") FROM table_77237 WHERE "Date" = '21/5/1997'
SELECT AVG("Against") FROM "table_77237" WHERE "Date" = '21/5/1997'