What was the Attendance at the Game with a Result of w 21 7?
CREATE TABLE table_6424 (
    "Week" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Record" text,
    "Game Site" text,
    "Attendance" real
)
SELECT AVG("Attendance") FROM table_6424 WHERE "Result" = 'w 21–7'
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 Attendance at the Game with a Result of w 21 7? ### Input: CREATE TABLE table_6424 (
    "Week" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Record" text,
    "Game Site" text,
    "Attendance" real
) ### Response: SELECT AVG("Attendance") FROM table_6424 WHERE "Result" = 'w 21–7'