The calculated distance (air line) between Cergy-Pontoise and Paris 12 Reuilly is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Paris 12 Reuilly is certainly longer, as only the direct route (as the crow flies) between Cergy-Pontoise and Paris 12 Reuilly has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles