so 88% counts for (20/22)*100 % of the mark in the class. Then, 55% counts for (2/22)*100 % of the mark. You want to multiply those portion percentages by the percentage of the class that created those averages respectively
55* ((2/22)*100 % and 88*...... (you fill in the rest on that one) then add them together.
This is at least how we would calculate our marks in our high school, and we are marked on varying assignments that are worth differnt percentages which seems to be similar to the scenario here. Anyone else correct me if I'm wrong.