For each station, return its longitude and the average duration of trips that started from the station.
SELECT T1.name ,  T1.long ,  avg ( T2.duration )  FROM station AS T1 JOIN trip AS T2 ON T1.id   =   T2.start_station_id GROUP BY T1.name
for each station refers to GROUP BY station name; return its longitude refers to selecting station longitude; average duration of trips that started from the station refers to AVG(trip.duration) WHERE trip.start_station_id = station.id;