Answer:
I tried my best to made the graph
3/-1/2
2/0/1
4/-2/3
2/0/1
1/+1/0
0/+2/1
Hopefully this will help you
I'm thinking maybe x is supposed to represent the number of tasks completed because it states Shelly earned 90 points on each task. Then when put together it may look like this, let's say there are 4 tasks= Ex.90 times the 4 tasks minus 20 points which would total the points Terrence's has earned. So i believe x is the total tasks. Hope I didn't make it confusing...
I want to say about 27% but I am not completely sure