The calculated distance (air line) between Daugavpils and Jēkabpils is approximately 50 miles respectively 80 kilometers.
By car or train, the actual journey to Jēkabpils is certainly longer, as only the direct route (as the crow flies) between Daugavpils and Jēkabpils has been calculated here.
Air line (approximately)
80 kilometers
43 nautical miles