What was the average attendance when the New York Mets were opponents with a record of 51-33?
CREATE TABLE table_name_81 (
    attendance INTEGER,
    opponent VARCHAR,
    record VARCHAR
)
SELECT AVG(attendance) FROM table_name_81 WHERE opponent = "new york mets" AND record = "51-33"
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: What was the average attendance when the New York Mets were opponents with a record of 51-33? ### Input: CREATE TABLE table_name_81 (
    attendance INTEGER,
    opponent VARCHAR,
    record VARCHAR
) ### Response: SELECT AVG(attendance) FROM table_name_81 WHERE opponent = "new york mets" AND record = "51-33"