John drives 1000 miles a month. He needs to get an oil change every 3000 miles. He gets 1 free oil change a year. If an oil change costs $50, how much does he pay a year? Think carefully first, then make a decision:
He needs to get an oil change every 3000 / 1000 = 3 months. So he gets 12 / 3 = 4 oil changes a year. That means he pays for 4 - 1 = 3 oil changes a year. So he pays 3 * $50 = $150 a year. So, the answer is 150.