Question 863449
Let x = number of questions on the test



She missed 4 questions, so she got x-4 questions correct.



84% of (number of questions on test) = number of correct answers



0.84x = x - 4



0.84x-x = -4



-0.16x = -4



x = -4/(-0.16)



x = 25



So there are <font size=4 color="red">25</font> questions total on the test. She missed 4 of them, so she got 25-21 = 24 questions correct. Notice how 21/25 = 0.84 ---> 0.84*100 = 84%