What is the number of attendance values for ties having an opponent of Middlesbrough and result of 3-1?
CREATE TABLE "fa_premier_league" (
  "date" text,
  "opponent" text,
  "venue" text,
  "result" text,
  "attendance" real
);
SELECT COUNT("attendance") FROM "fa_premier_league" WHERE "opponent"='middlesbrough' AND "result"='3-1';