Answer:
74 adult tickets
Explanation:
Create a system of equations where a is the number of adult tickets and c is the number of child tickets:
a + c = 238
17a + 14c = 3554
Solve by elimination by multiplying the top equation by -14:
-14a - 14c = -3332
17a + 14c = 3554
Add these together, and solve for a:
3a = 222
a = 74
So, 74 adult tickets were sold last night