Which Week has an Opponent of baltimore colts, and an Attendance smaller than 55,137?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "opponent" text,
  "result" text,
  "game_site" text,
  "attendance" real
);
SELECT AVG("week") FROM "schedule" WHERE "opponent"='baltimore colts' AND "attendance"<'55,137';