What is the average number of goals conceded where more than 19 goals were scored, the team had 31 points, and more than 7 draws?
CREATE TABLE "clausura_2007_standings" (
  "place_posici_n" real,
  "team_equipo" text,
  "played_pj" real,
  "won_pg" real,
  "draw_pe" real,
  "lost_pp" real,
  "goals_scored_gf" real,
  "goals_conceded_gc" real,
  "dif" real,
  "points_pts" real
);
SELECT AVG("goals_conceded_gc") FROM "clausura_2007_standings" WHERE "goals_scored_gf">19 AND "points_pts"=31 AND "draw_pe">7;