When has a Result of l 27-7 and an Opponent of at minnesota vikings?
CREATE TABLE "schedule" (
  "week" real,
  "date" text,
  "opponent" text,
  "result" text,
  "venue" text,
  "attendance" text
);
SELECT "date" FROM "schedule" WHERE "result"='l 27-7' AND "opponent"='at minnesota vikings';