What is the average share for episodes with over 7.82 viewers, ranks of 3 and a weekly rank of 54?
CREATE TABLE "u_s_nielsen_ratings" (
  "episode" text,
  "rating" real,
  "share" real,
  "rating_share_18_49" text,
  "viewers_millions" real,
  "rank_timeslot" text,
  "rank_night" text,
  "rank_week" text
);
SELECT AVG("share") FROM "u_s_nielsen_ratings" WHERE "viewers_millions">7.82 AND "rank_timeslot"='3' AND "rank_week"='54';