Answer:
children = 67
Step-by-step explanation:
two equations can be derived from this question
x + y = 85 equation 1
3x + y = 121 equation 2
where x = number of adults
y = number of children
subtract equation 1 from 2
2x = 36
x = 18
substitute for x in equation 1
y = 85 - 18 = 67