What was the average attendance when the opponent was at Philadelphia Eagles and the week was later than week 6?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "opponent" text,
  "result" text,
  "tv_time" text,
  "attendance" real
);
SELECT AVG("attendance") FROM "schedule" WHERE "week">6 AND "opponent"='at philadelphia eagles';