deanna gets 3 problema incorrect on her math quiz. her score is 85%. how many questions are on the quiz

Let's start by seeing what percentage is incorrect.
100-85=15
So, 15% is incorrect when answering 3 problems wrong. So let's divide 15 by 3.
15÷3=5
So, each problem is worth 5%, let's divide 100 by 5. The reason I'm doing thiis is to find how many questions are on the quiz, since if you got them all right, it's 100.
100÷5
20
There are 20 questions, let's make sure this is correct.
If she got 3 wrong, she got 17 right. Let's calculate her percentage and make sure it is the right one.
17÷20
.85×100
85%
So, there are 20 questions on the math quiz.