Answer: Did not convert the minutes to hours
Explanation:
The most obvious mistake here would be to not convert the minutes into hours.
Remember, the speed given, (7.5), is in miles per HOUR. Your time is given in MINUTES. a conversion is required. 45 minutes are 45/60 = 0.75 hrs.
NOW you can use S = DT to find your distance:
7.5 = D/0.75
.: D = 5.625 miles