How many different brief descriptions are there for crashes with 0/161 fatalities?
CREATE TABLE "table1_229917_2" (
  "date_dd_mm_yyyy" text,
  "tail_number" text,
  "location" text,
  "fatalities" text,
  "brief_description" text
);
SELECT COUNT("brief_description") FROM "table1_229917_2" WHERE "fatalities"='0/161';