When the Country is Mexico, Women's race is less than 0, and Men's race is more than 0, what's the average total?
CREATE TABLE "victories_by_nationality" (
  "country" text,
  "men_s_race" real,
  "women_s_race" real,
  "men_s_wheelchair" real,
  "women_s_wheelchair" real,
  "total" real
);
SELECT AVG("total") FROM "victories_by_nationality" WHERE "men_s_race">0 AND "country"='mexico' AND "women_s_race"<0;