The calculated distance (air line) between Pyeongchang and Gwangmyeong is approximately 84 miles respectively 135 kilometers.
By car or train, the actual journey to Gwangmyeong is certainly longer, as only the direct route (as the crow flies) between Pyeongchang and Gwangmyeong has been calculated here.
Air line (approximately)
135 kilometers
73 nautical miles