what is the average silver when the total is more than 20?
CREATE TABLE table_50716 (
    "Rank" real,
    "Nation" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real,
    "Total" real
)
SELECT AVG("Silver") FROM table_50716 WHERE "Total" > '20'
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 is the average silver when the total is more than 20? ### Input: CREATE TABLE table_50716 (
    "Rank" real,
    "Nation" text,
    "Gold" real,
    "Silver" real,
    "Bronze" real,
    "Total" real
) ### Response: SELECT AVG("Silver") FROM table_50716 WHERE "Total" > '20'