What is the average Loss for the long of more than 12 with a name of opponents with a Gain larger than 1751?
CREATE TABLE "rushing" (
  "name" text,
  "gp_gs" text,
  "gain" real,
  "loss" real,
  "long" real,
  "avg_g" text
);
SELECT AVG("loss") FROM "rushing" WHERE "long">12 AND "name"='opponents' AND "gain">1751;