Answer:
23.5 miles a gallon, and $18.90 trip cost.
Explanation:
16 is the full tank, and 6 is 3/8ths of that, so 6 gallons were used during the trip.
Miles per gallon:
141/6 = 23.5
The fuel mileage was 23.5 miles a gallon.
Cost:
6 * 3.15 = 18.9
The cost of the trip was $18.90.