Urban areas developed subways, elevated trains, and streetcar systems because if all commuters rode in cars it would cause traffic jams and major traffic. It made it easier for people to move around in bigger cities.
Survival of the fittest will survive
Answer:
Their numbers could be 1 and 14, 13 and 2, 12 and 3, 11 and 4, 10 and 5, 9 and 6, 8 and 7, 7 and 8, or 6 and 9.