<PRE><B>Question 252697</B>
Firstly, we note that 11 students take both music and algebra.

Hence, this means, that out of the 24 students enrolled for Algebra, 11 of the also take music.
24 - 11 = 13.
Therefore, only 13 students only take Algebra. 

Also, this means, that out of the 49 students enrolled in music, 11 of the also take algebra.
49-11= 38.
Therefore, only 38 students only take Music.

The total amount of students enrolled in these two classes are:-
Algebra only = 13
Music only = 38
Algebra and Music = 11

This gives a total of 13+38+11 = 62 students that are enrolled in the two courses.

Since there are 80 students in the school.
We subtract the 62 students in the two courses from the entire student roll.
80 - 62 = 18
Therefore, 18 students are NOT in either algebra or music. </PRE>