How many different integers represent the sum of two or more members of the set {-4, -3, -2, -1 , 0, 1, 2, 3, 4}?
What is the biggest sum?
What is the smallest sum?
So there is at the most how many totals?
I'd write all thes out in a row and then cross them off when I find a sum that adds to that number.
Ultimately all the crossed numbers are possible sums. So count them.