a) 45km for 4 hours and 15min (4.25 hours) = 45 / 45.25 ~= 10.58 km/h
b) From 4:15 to 5 = 45min
c) 45km for 3 hours (5:00 to 8:00) = 45 / 3 = 15 km/h
NOTE!
The author actually wanted the answer on A) to be 10 km/h and the journey to be 4.5 hours (4 hours 30min) but instead they made it 4.25 (as shown on the graph, since 1 square is 30 minutes).
