Which 1990-1991 is the average one that has Played of 38, and Points of 40?
CREATE TABLE "relegation" (
  "team" text,
  "average" real,
  "points" real,
  "played" real,
  "1988_89" text,
  "1989_90" text,
  "1990_1991" real
);
SELECT AVG("1990_1991") FROM "relegation" WHERE "played"=38 AND "points"=40;