What is the average number of silver medals of the nation with 3 bronzes and more than 4 total medals?
CREATE TABLE "medal_table" (
  "rank" text,
  "nation" text,
  "gold" real,
  "silver" real,
  "bronze" real,
  "total" real
);
SELECT AVG("silver") FROM "medal_table" WHERE "bronze"=3 AND "total">4;