Calculate Complex Average calculation with weight from four tables

Actually understanding the requirement is itself difficult just by reading.

I want to calculate average of scores each branch with weight from subject table for all the titles in Result table like below

Average for each branch =Sum of all (sum of scores for each weight * weight) for each branch/sum of weights for all the titles of that branch

For example for branch id 2 it's,

Sum of scores for weight 4 ( subject id 3) is 10 and sum of scores for weight 5 (subject id 4 and 5) is (2+1+2+3)=8

So there are 5 titles in result table for branch id 2

Average score for branch 2 = {(10*4)+(8*5)} / {(4)+(5*4)} = 3.33

I know it's little difficult to understand