CREATE TABLE table_31756 ("Year" FLOAT, "Class" TEXT, "Team" TEXT, "Points" FLOAT, "Rank" TEXT, "Wins" FLOAT)

Tell me the average wins for class of 50cc and rank of 8th
SELECT AVG("Wins") FROM table_31756 WHERE "Class" = '50cc' AND "Rank" = '8th'
SELECT AVG("Wins") FROM "table_31756" WHERE "Class" = '50cc' AND "Rank" = '8th'