If you have built 25 cars, and they are 36 dollars per, then multiply 25 and 36 for the amount of money. This will result with 25*36=900. Since we already have 900 dollars worth, we subtract that from the goal of 1620, leaving us with 1620-900=720. Now, divide this by the price per car for the amount of cars needed to get to this goal. 720/36=20 cars
Hope this helps!
