Since she answered 90% of her quiz correct, that means if she were to answer 10 questions, 9 would be correct. Lucky for us, 50 is a multiple of 10. If you multiply 10 by 5, you'd get 50. You would also need to multiply 9 by 5 as well. When you do this you'd get
45/50 correct. (divided them to make sure you get .90 if so, I'm right :)
