Answer:
646 child tickets are sold
Explanation:
Let c represent the number of child tickets sold. Then (c-186) is the number of student tickets sold, and (c+234) is the number of adult tickets sold. The total number sold is ...
(c -186) + c + (c+234) = 1986
3c +48 = 1986 . . . simplify
c + 16 = 662 . . . . divide by 3
c = 646 . . . . . . . . . subtract 16
The number of child tickets sold is 646.