HELP ASAP! Can someone please help me with this problem. I tried inputting the numbers to find the mean but I did not get the right answer. Can someone please help me with the last box? Thank you for your time!

Barrett is comparing the membership fees for two museums.the art museum charges a one-time fee of $8.25 plus $2.25 per month. the science museum charges a one-time fee of $10.75 plus $3.50 per month. how much does barrett save by joining the art museum instead of the science museum?