In Which rank was there a location of porto alegre?
CREATE TABLE "brazil_s_15_busiest_airports_by_passenge" (
  "rank" real,
  "location" text,
  "total_passengers" real,
  "annual_change" text,
  "capacity_in_use" text
);
SELECT "rank" FROM "brazil_s_15_busiest_airports_by_passenge" WHERE "location"='porto alegre';