Hi i hope i am putting this question in the correct forum so here goes.

Say someone has taken 4 tests over the year one test had 20 questions one had 54 questions one had 40 questions and a practical exam that represents 20% of the total mark.

If i have 4 percentages say 80%,70%,65% and 60%on the practical how do i add these numbers together to represent one total percentage.

I am no good at math and my son has asked me this question could someone please give me the formula and an explanation so as i may explain this to my son thank you.