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 be71<=x<=98
For the graph, I don't really understand. I think you just graph 71<=x<=98.