Final answer:
To find the number of liters of synthetic oil, subtract the amount of natural oil from the total amount of oil.
Step-by-step explanation:
To find out how many liters of synthetic oil you have, you need to subtract the amount of natural oil from the total amount of oil. In this case, you have 837 liters of oil, 4 liters of which are natural oil. So, to find the number of liters of synthetic oil, subtract 4 from 837:
837 - 4 = 833 liters of synthetic oil