The cost of just the car (without commission) is smaller than $41,000, so if you compare 2.5% of $41,000 and 2.5% of the price of the car, the former (2.5% of $41,000) will actually be bigger. That's why subtracting 2.5% of $41,000 from $41,000 gives the wrong answer, because this amount is more than the commission that the salesman makes. He only get 2.5% of the price of the car.
I hope this helps! It's great to see you on here almost every day, and I can't wait to see how much you will have improved by the end of the course! 🙂