What is the average silver that has a gold greater than 3, with soviet union (urs) as the nation, and a bronze greater than 26?
CREATE TABLE "women" (
  "rank" real,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("silver") FROM "women" WHERE "gold">3 AND "nation"='soviet union (urs)' AND "bronze">26;