Guseo-dong to airport, best way?

Does anyone know the best way to get to the airport from Guseo-dong or any of the areas around there? All I can think of is taking a taxi, but don't know how much that will set me back. Thanks.

Taxi isn't too bad - around

Taxi isn't too bad - around 15,000 for your troubles - or you could take the subway, change at Yonsan-dong and get off at Deokcheon for a much cheaper taxi!