What year was the Competition of World Junior Championships with a 20th (qf) position?
CREATE TABLE table_name_18 (
    year INTEGER,
    competition VARCHAR,
    position VARCHAR
)
SELECT AVG(year) FROM table_name_18 WHERE competition = "world junior championships" AND position = "20th (qf)"
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 year was the Competition of World Junior Championships with a 20th (qf) position? ### Input: CREATE TABLE table_name_18 (
    year INTEGER,
    competition VARCHAR,
    position VARCHAR
) ### Response: SELECT AVG(year) FROM table_name_18 WHERE competition = "world junior championships" AND position = "20th (qf)"