I think what you have to do here is first find out how many each student of each group gets. So, let's start off with how many oatmeal muffins each of the 8 students get. To do this, divide the 12 oatmeal muffins by 8, which gets you 1.5 oatmeal muffins per student.
Then, find out how many Apple muffins each of the 6 students get. To do this, divide the 15 Apple muffins by the 6 students, which leaves us with 2.5 Apple muffins per student.
Since Carmine is in both groups, she receives an equal share of both types of muffins. You add the 1.5 oatmeal muffin and 2.5 Apple muffins to see that Carmine gets 4 muffins in total. I hope this helped :)
