Name the 18-49 rating for weekly rank of 30
CREATE TABLE "weekly" (
  "episode" text,
  "air_date" text,
  "timeslot" text,
  "households_rating_share" text,
  "18_49_rating_share" text,
  "viewers_m" real,
  "weekly_rank_num" text
);
SELECT "18_49_rating_share" FROM "weekly" WHERE "weekly_rank_num"='30';