The calculated distance (air line) between Šentilj v Slov. Goricah and Brežice is approximately 54 miles respectively 87 kilometers.
By car or train, the actual journey to Brežice is certainly longer, as only the direct route (as the crow flies) between Šentilj v Slov. Goricah and Brežice has been calculated here.
Air line (approximately)
87 kilometers
47 nautical miles