-1 Let S represent the students taking Spanish, C the students taking Chinese, and N the students taking neither language. S+C+N is a constant, as is well known.
At the outset, S+C+N0=N.
After having ten students withdraw from Chinese class, the final enrollment is S+C10+N1.
It is also known that N1 = N0 + 4.
To see what happens when we plug the second equation into the first, we do the following:
S+C−10+N0+4=N0
S+C−6=N0
When we take the difference between the first and third equations, we get:
S+C+N0−(S+C−6)=N−(N0+4)
6=4
As a result, there are now 4 fewer students who choose Spanish over Chinese.
But that is not the case. Since there are now 4 more students who take neither Spanish nor Chinese, the number of those who take only Spanish cannot decrease by 4. It's likely that there are now four more students than before who choose Spanish over Chinese.
Possible reasons for the discrepancy are as follows:
Ten of the former Chinese students may have been enrolled in Spanish as well.
It's possible that the four students who initially enrolled in neither class are actually taking Spanish as well.
It's safe to assume that there are now four more students opting for Spanish over Chinese. FLYINGTOGETHER