Final answer:
Felix served 3/5 of a gallon more hot chocolate than apple cider.
Step-by-step explanation:
To find out how much more hot chocolate Felix served than apple cider, we need to subtract the amount of apple cider from the amount of hot chocolate.
Given that Felix served 9/10 of a gallon of hot chocolate and 3/10 of a gallon of apple cider, we can calculate the difference by subtracting 3/10 from 9/10.
9/10 - 3/10 = 6/10, which simplifies to 3/5. Therefore, Felix served 3/5 of a gallon more hot chocolate than apple cider.