Darnell's car used 8 gallons of gasoline to travel 340 miles. after a mechanic work on teh car, it used 7 gallons of gasoline to travel 350 miles. if the price of gasoline was approximately $4.00 per gallon, how much less to the nearest cent per mile, did it cost to run the car after the mechanic worked on it?

 What we are going to do for this case is find the cost for each case:
 Cost to run the car before the mechanic worked on it:
 
 Cost to run the car after the mechanic worked on it:
 
 The difference between both cases is:
 
 
 It cost to run the car after the mechanic worked on it 0.01 $ / mile less than before the mechanic worked on it.