What is the earliest year with less than 45 points for Yamaha team in 21st rank?
CREATE TABLE "grand_prix_motorcycle_racing_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "rank" text,
  "wins" real
);
SELECT MIN("year") FROM "grand_prix_motorcycle_racing_results" WHERE "points"<45 AND "team"='yamaha' AND "rank"='21st';