SELECT AVG("Yards") FROM table_36799 WHERE "Average" < '4' AND "Long" = '12' AND "Attempts" < '29'
What is the average Yards with an average of less than 4 and the long is 12 with less than 29 attempts?
CREATE TABLE table_36799 (
    "Player" text,
    "Attempts" real,
    "Yards" real,
    "Average" real,
    "Long" real,
    "Touchdowns" real
)