Answer 19:1
Work:
Students scoring above 80 -
9+18+72+15= 114
Students score exactly 80-
6
114/6 = 19
19 students scored above 80 for every 1 student that scored exactly 80.
You would have to add a positive 6 to the negative 6 to get zero. Lets say you have -2 in order to get it to zero or just any positive number, you have to add a positive of the same value or higher to be able to get it there. I hope you understand that.