answer:I’m trying to answer as a person skilled in math, not economics, so if I use any false premises here due to ignorance of economics, someone please jump in and correct me! Okay, so it seems to me that there is a particular amount charged before any work is done at all. I would assume that is what is meant by a fixed cost. It seems you’ve figured out the fixed cost already: it costs $100 to clean 0 rooms, so $100 must be the charge accumulated before any work is done, or the fixed cost. That’s a good start. Look at the next set of numbers. $200 for 3 rooms. You know that $100 of that is the fixed cost, the amount charged before any work is completed at all. So the other $100 is the price of the work of three rooms, or the variable cost. Can you use this information to determine what the total variable cost is? Again someone please correct me if my ignorance of economics is causing me to go about this incorrectly. Really sorry if I’m leading you astray; just answering using my mathematical intuition.