What is the average operation beginning with a length of ampang and over 27 stations?
CREATE TABLE table_name_12 (began_operation INTEGER, length__km_ VARCHAR, stations VARCHAR)
SELECT AVG(began_operation) FROM table_name_12 WHERE length__km_ = "ampang" AND stations > 27
### Context: CREATE TABLE table_name_12 (began_operation INTEGER, length__km_ VARCHAR, stations VARCHAR) ### Question: What is the average operation beginning with a length of ampang and over 27 stations? ### Answer: SELECT AVG(began_operation) FROM table_name_12 WHERE length__km_ = "ampang" AND stations > 27