SCHEMA:
CREATE TABLE table_name_74 (laps INTEGER, rider VARCHAR, grid VARCHAR, bike VARCHAR)
USER:
Tell me the average Laps for grid larger than 12 and bikes of ducati 999rs for dean ellison

QUERY:
SELECT AVG(laps) FROM table_name_74 WHERE grid > 12 AND bike = "ducati 999rs" AND rider = "dean ellison"