The calculated distance (air line) between Pyeongtaek and Yangp'yŏng is approximately 41 miles respectively 66 kilometers.
By car or train, the actual journey to Yangp'yŏng is certainly longer, as only the direct route (as the crow flies) between Pyeongtaek and Yangp'yŏng has been calculated here.
Air line (approximately)
66 kilometers
35 nautical miles