SO... I believe if I understand the question that he drive to work 5 times a week w/ 7 gallons round trip. 5x7= 35 miles; now, since there saying in a month i will have to assume there a four weeks per month. so 35 miles per week x 4 weeks = 140 miles. then they say you also drive and extra 25 miles during this period bringing you to a grand total of 165 miles.
So what i did was knowing the cost would be 3.15 for every 20 miles for every gallon, I found out what 5 miles would cost instead of 20 -- 25% of 3.15 = $0.7875 . 165 miles x $0.07875 = total of $129.9 I believe this to be correct, however i'am not positive. hope this helps
