How many yards were averaged by the player that had a higher than 13 average with less than 18 long?
CREATE TABLE "wide_receivers" (
  "player" text,
  "rec" real,
  "yards" real,
  "avg" real,
  "td_s" real,
  "long" real
);
SELECT AVG("yards") FROM "wide_receivers" WHERE "long"<18 AND "avg">13;