The calculated distance (air line) between Tung Chung and Mong Kok is approximately 15 miles respectively 24 kilometers.
By car or train, the actual journey to Mong Kok is certainly longer, as only the direct route (as the crow flies) between Tung Chung and Mong Kok has been calculated here.
Air line (approximately)
24 kilometers
13 nautical miles