Answer:
20
Explanation:
For the mean to be 21, the total of the 5 numbers must be 21*5= 105
To find what the final quiz score must be, we need to subtract the first 4 scores from 105. 105- 21- 24- 23- 17= 20
We can check this answer by finding the median of the 5 numbers now (17,20,21,24,23). The new median is 21 which means the final quiz score must be 20!
Hope this helped! :)