100 ÷ 25 = 4
So, each question is worth 4 points.
100 - 84 = 16
16 ÷ 4 = 4 (questions)
So, she got 4 questions wrong
25 - 4 = 21
So, she got 21 questions wrong
To double check do this,
21 x 4 = 84%
100 - 84% = 16%
So, she got 16% of her questions wrong
In conclusion, "She got 4 question incorrect and 21 questions correct and 16% of her questions were incorrect".
Hope this helps! :D