Question 929457
Assuming the quizzes are equally weighted:


Let s = # quiz scores before the 5 scores of 100. Then 84s = sum of the scores, and 84s + 5*100 = 84s + 500 = the sum of her scores afterwards.


She now has s+5 quiz scores, so (84s + 500)/(s+5) = 92. Solving, s = 5.


Another way to see that she had 5 scores beforehand is to note that 92 is exactly halfway between 84 and 100.