Tell me the average wins for class of 50cc and rank of 8th
CREATE TABLE table_31756 (
    "Year" real,
    "Class" text,
    "Team" text,
    "Points" real,
    "Rank" text,
    "Wins" real
)
SELECT AVG("Wins") FROM table_31756 WHERE "Class" = '50cc' AND "Rank" = '8th'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: Tell me the average wins for class of 50cc and rank of 8th ### Input: CREATE TABLE table_31756 (
    "Year" real,
    "Class" text,
    "Team" text,
    "Points" real,
    "Rank" text,
    "Wins" real
) ### Response: SELECT AVG("Wins") FROM table_31756 WHERE "Class" = '50cc' AND "Rank" = '8th'