What is the 1991 when 1997 is 18?
CREATE TABLE table_64586 (
    "Tournament" text,
    "2000" text,
    "1999" text,
    "1998" text,
    "1997" text,
    "1996" text,
    "1995" text,
    "1994" text,
    "1993" text,
    "1992" text,
    "1991" text
)
SELECT "1991" FROM table_64586 WHERE "1997" = '18'
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 1991 when 1997 is 18? ### Input: CREATE TABLE table_64586 (
    "Tournament" text,
    "2000" text,
    "1999" text,
    "1998" text,
    "1997" text,
    "1996" text,
    "1995" text,
    "1994" text,
    "1993" text,
    "1992" text,
    "1991" text
) ### Response: SELECT "1991" FROM table_64586 WHERE "1997" = '18'