This is a straightforward scale conversion problem.
Actual Distance = Map Distance × Scale Factor
Actual Distance = 5.5 in × 0.5 mi/in
Actual Distance = 2.75 miles
The actual distance between the two towns is 2.75 miles.
The question asks "what actual towns?"—this cannot be answered from the information given. The calculation only yields the distance, not the identity of the towns.