Answer: the average speed is 7.5 mph or at least im pretty sure
Step-by-step explanation:
This is because if you make the 2 miles at 6 mph to 1 mile at 3 mph then you get 1 mile at 3mph and 1 mile at 12 mph. now that you have the unit rates of these you can add them. 1 + 1 = 2 miles and 3 + 12 = 15 mph now divide this by two and you get 7.5 mph per mile.
I hope this helped, if it did could you give me a good rating? lol