If n is the number of students, 3n/7+8 enjoyed the fireworks.
That leaves n-(3n/7+8)=4n/7-8.
A quarter of these is n/7-2, the number who enjoyed the singing.
The number of students remaining is 36=n-(3n/7+8+n/7-2),
36=n-4n/7-6
36=3n/7-6,
42=3n/7,
14=n/7, n=98. There were 98 students in the survey.