The calculated distance (air line) between Pyeongchang and Pyeongtaek is approximately 76 miles respectively 123 kilometers.
By car or train, the actual journey to Pyeongtaek is certainly longer, as only the direct route (as the crow flies) between Pyeongchang and Pyeongtaek has been calculated here.
Air line (approximately)
123 kilometers
66 nautical miles