How many years had a location at Forest Hills and a score of 6–3, 6–3 for John McEnroe?
CREATE TABLE "singles" (
  "location" text,
  "year" real,
  "champion" text,
  "runner_up" text,
  "score" text
);
SELECT COUNT("year") FROM "singles" WHERE "location"='forest hills' AND "runner_up"='john mcenroe' AND "score"='6–3, 6–3';