Answer:
9 child tickets and 17 adult tickets were sold.
Explanation:
Let the number of adult tickets sold be 

and the number of child tickets be 
 .
.
The theater sold a total number of 26 tickets. 
This means that: 
 .....eqn1
.....eqn1
The theater made a total sale od $194.
This implies that:
 ...eqn2
...eqn2
We make 
 the subject in equation 1:
 the subject in equation 1: 
 ...eqn3
...eqn3
Substitute equation (3) into equation (2)

Expand to get: 





Put c=9 into equation (3) to get:

Therefore 9 child tickets and 17 adult tickets were sold.