Answer:
350
Explanation:
Okay, so we have a total of 639 tickets that they were sold. Using both students and adults tickets.
And also we know that the students r 61 fewer than the adults. So X minus 61. 
X -61 = 289. 
350 -61= 289 
 It's gonna be a total of 289. And we can check our results, X plus Y. So 350 plus 289. It's gonna be a total of 639.