What is the average of goals against, where overall goals are more than 35 and the goal difference is 20?
CREATE TABLE "final_table" (
  "position" real,
  "club" text,
  "played" real,
  "points" text,
  "wins" real,
  "draws" real,
  "losses" real,
  "goals_for" real,
  "goals_against" real,
  "goal_difference" real
);
SELECT AVG("goals_against") FROM "final_table" WHERE "goals_for">35 AND "goal_difference"=20;