I'm not quite understanding how to solve these word problems

I'll help you on the first one.
Anya test scores are 78 and 91.
She has one more test and want to average between an 80-89 inclusive.
Lets set up a inequality and call the remaining test x.
80<=(78+91+x)/3<=89
Multiply everything by 3
240<=169+x<=267
Subtract 169 from everything
71<=x<=98
In interval notation that would be [71,98]
In set notation that would be{x|71<=x<=98}
For the graph, I don't really understand. I think you just graph 71<=x<=98.

I'm not sure exactly but my best guess would be 1/4