It's best to convert the hours to minutes to not get confused. 50/60 because you want to find how far it can travel in a minute for part a). And then you multiply by 90 because 1.5 hours = 90 minutes. 1.5 hours = 60 mins + (0.5/60mins) = 90 mins. Then part b) is more straightforward and he travelled for exactly 2 hours at a constant speed of 65km.