The following table shows the total number of students in four different classes of a school, and the percentages of students participating in Music or Plays from each of these four different classes. NO student participates both in Music and in Plays.

What is the total number of students who do NOT participate in Music or Plays from classes X and VII, taken together?

Total number of students from classes X and VII, taken together = 600+250

= 850    Eq.(i)

Total number of students who participate in Music or Plays from classes X and VII, taken together = 600 of (12+8)% +250 of (10+12)%

= 600 of 20% +250 of 22%

= $$600\times\frac{20}{100}+250\times\frac{22}{100}$$

= $$120+55$$

= 175     Eq.(ii)

total number of students who do NOT participate in Music or Plays from classes X and VII, taken together = Eq.(i)-Eq.(ii)

= 850-175

= 675