Aused car costs $5,000. you figure you can get 2 years out of it. you drive 12,000 miles per year. your car insurance cost $1,500 per year. you figure you will spend $400 per year on maintenance. gas cost $2.50 per gallon, and car gets 20 miles per gallon. what will your average cost per mile after 2 years?

Since the value of the car is not specified after 2 years, we will assume it is zero.

Then the total cost is

... car cost + 2×(insurance cost + maintenance cost + gas cost)

... = 5000 + 2×(1500 + 400 + (12000/20*2.50))

... = 5000 + 2×(1900 + 1500)

... = 11,800

This is the cost for driving 24,000 miles, so the cost per mile is

... 11,800/24,000 ≈ 0.49167

Your average cost per mile will be about $0.49.

The purchase price of the car is about 42% of that cost, so the operating cost is reduced somewhat if there is resale value at the end of 2 years.

Answer

y = (1/4)x - 5                 or     4y - x + 20 = 0

Explanation

To get the rule required, we interpret the sentence and write it in a mathematical form.

5 less than one fourth of x is y  

one fourth of x ⇒ (1/4)x

5 less than one fourth of x is y  ⇒  (1/4)x - 5 = y

y = (1/4)x - 5

4y = x - 20

4y - x + 20 = 0