What is the average win as a percentage of German racer Rudi Altig, who has ridden in over 79 races?
CREATE TABLE "highest_number_of_six_day_victories" (
  "name" text,
  "nationality" text,
  "races_won" real,
  "races_ridden" real,
  "win_average" real
);
SELECT AVG("win_average") FROM "highest_number_of_six_day_victories" WHERE "nationality"='german' AND "name"='rudi altig' AND "races_ridden">79;