What is the number of podiums for the races of 13/15?
CREATE TABLE "champions" (
  "season" real,
  "series_name" text,
  "champion" text,
  "races" text,
  "pole_positions" text,
  "wins" text,
  "podiums" text,
  "fastest_laps" text,
  "points" text,
  "margin_pts" text
);
SELECT "podiums" FROM "champions" WHERE "races"='13/15';