What's the number of the episode directed by Tucker Gates?
CREATE TABLE "table1_12722302_3" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "bens_location" text,
  "original_air_date" text,
  "u_s_viewers_million" text
);
SELECT "no" FROM "table1_12722302_3" WHERE "directed_by"='Tucker Gates';