Because he drove 1542.75 miles in 3 days, you would have to divide 1542.75 by 3 to figure out how many miles he drove in one day.
1542.75/3 = 514.25
Then to figure out how many miles he drove per hour, you would divide 514.25 by 8.5, which is the same as 8 1/2 hours.
514.25/8.5 = 60.5
So the answer is 60.5 mph