CREATE TABLE table_64473 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Attendance" FLOAT)

How many people attended the September 21, 1980 game?
SELECT AVG("Attendance") FROM table_64473 WHERE "Date" = 'september 21, 1980'
SELECT AVG("Attendance") FROM "table_64473" WHERE "Date" = 'september 21, 1980'