Let the 5 test scores be a, b, c, d, and e. Let m be the average. To find the average of the 5 scores, add them, and divide the sum by 5.

believe the answer is 8 because sulfur has 6 valence electrons and when it becomes sulfide it gains two electrons making it 6+2=8.
They’re all adding 5, so 18+5=23
So I think 23