Answer:
Number of chaperones on the trip were 12.
Explanation:
Let there were x students on the trip.
Number of chaperones on 20 students = 3
Therefore, number chaperones required for x students = 

Total number persons = Number of students + Number of chaperones 
 = x + 

 = 

Since number of persons on the trip has been given as 92.
92 = 

x = 

 = 80
Therefore, number of students on the trip are 80.
And number of chaperones on the trip = 92 - 80 = 12