CREATE TABLE table_78612 ("Week" FLOAT, "Date" CLOB, "Opponent" CLOB, "Result" CLOB, "Attendance" FLOAT)

What is the attendance for the game against the Kansas City Chiefs earlier than week 13?
SELECT AVG("Attendance") FROM table_78612 WHERE "Opponent" = 'kansas city chiefs' AND "Week" < '13'
SELECT AVG("Attendance") FROM "table_78612" WHERE "Opponent" = 'kansas city chiefs' AND "Week" < '13'