Answer: 81
Explanation:
Given : The percentage of students chose to study French their sophomore year = 91%
Let the total number of students b x.
Since , there were 819 such students that chose to study French their sophomore year
According to the question , we have
91% of (x)= 819

Now , the number of students chose not to take French their sophomore year : 900- 819= 81
Hence, the students chose not to take French their sophomore year= 81