The calculated distance (air line) between Morlanwelz-Mariemont and Mons is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Mons is certainly longer, as only the direct route (as the crow flies) between Morlanwelz-Mariemont and Mons has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles