How many seasons feature essendon, and a Score of 15.12 (102) – 9.14 (68)?
CREATE TABLE "back_to_back_night_pre_season_winners" (
  "season" real,
  "premier" text,
  "runner_up" text,
  "score" text,
  "venue" text,
  "attendance" real,
  "margin" real
);
SELECT COUNT("season") FROM "back_to_back_night_pre_season_winners" WHERE "premier"='essendon' AND "score"='15.12 (102) – 9.14 (68)';