A car traveling from town A to town B at an average speed of 80 km/h took 54 minutes. Another car took 40 minutes to travel the same distance. What was the difference in their speed in km/h?

distance=speed*tim

it is the same distance, so
80km/hr*54=S*40
S=80*(54/40)
difference: 80(54/40 -1)=80*14/40_=28km/hr