you have to subtract the initial cost of the car from $270. That leaves you with $210 remaining to spend on mileage. At a rate of 50 cents per mile you have to determine how many miles it would take to spend $210. At a rate of $1 per mile it would take 210 miles to spend $210 dollars. BUt since each mile is 50 cents and it takes .50 times 2 to make 1, you have the multiply 210 by 2 which equals 420.
