17. There are two groups of students. There are x students in the first group and each student came make m cakes in an hour. There are y students in the first group and each student came make n cakes in an hour. How many cakes can each student make among the two groups?
In total group 1 makes xm cakes per hour
In total group 2 makes yn cakes per hour
so altogether they make (xm+yn) cakes per hour,
On average this is (xm+yn)/(x+y) cakes per student per hour.
I think that is what the question is asking for but the working is not very clear....