The calculated distance (air line) between Duba-Yurt and Makhachkala is approximately 90 miles respectively 144 kilometers.
By car or train, the actual journey to Makhachkala is certainly longer, as only the direct route (as the crow flies) between Duba-Yurt and Makhachkala has been calculated here.
Air line (approximately)
144 kilometers
78 nautical miles