Part/Whole=Percent/100
Part=26
Whole=30
Percent= Variable because that is what you want to find out
So now it is 26/30=X/100
You then cross multiply and you get
2600=30X
Divide by 30 and your answer is 86.66667. She got 86.66667% of her questions right. I am not sure if you need to round that or not.
Another way you can do it is Divide 26÷30=.866667 and then multiply by 100 to get 86.66667.