Calculating average speed

Average speed (mph) = Total Distance (m)/Total time (h)

Total distance = speed x mins/60

Part 1: 12mph x 1/6 (10 mins = 1/6 of an hour) = 2 miles

Part 2: 20mph x 1/4 (15 mins = 1/4 of an hour) = 5 miles

Total time = 1/6 of an hour + 1/4 an hour = 5/12 of an hour

7/(5/12 of an hour) = 16.8mph 

Tota distance over combined head to head speed 120/150

time to meet is 12/15 of an hour = 48mins

e) "What is being asked?" The question wants you to calculate a distance that is shared between two vehicles. 

t=120/150

the distance they meet must be 

Distance travelled = Total Distance (m)/Total time (h) so

Total Distance (m) = 

So both meet at a distance called x which for the car is X and fo the lorrt is 120-x