Davids car used 8 gallons of gasoline to travel 340 miles. after a mechanic worked on the car it used 7 gallons 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 his car after the mechanic worked on it

The answe maybbe

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.