What is the average decile of the school with a state authority and a roll number of 888?
CREATE TABLE table_10897 (
    "Name" text,
    "Years" text,
    "Gender" text,
    "Area" text,
    "Authority" text,
    "Decile" real,
    "Roll" real
)
SELECT AVG("Decile") FROM table_10897 WHERE "Authority" = 'state' AND "Roll" = '888'
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 decile of the school with a state authority and a roll number of 888? ### Input: CREATE TABLE table_10897 (
    "Name" text,
    "Years" text,
    "Gender" text,
    "Area" text,
    "Authority" text,
    "Decile" real,
    "Roll" real
) ### Response: SELECT AVG("Decile") FROM table_10897 WHERE "Authority" = 'state' AND "Roll" = '888'