What is the average 10K wins the United States, which had 0 5K wins, have?
CREATE TABLE "multiple_winners" (
  "runner" text,
  "country" text,
  "5_k_wins" real,
  "10_k_wins" real,
  "total" real
);
SELECT AVG("10_k_wins") FROM "multiple_winners" WHERE "country"='united states' AND "5_k_wins"=0;