Answer: 168 adult tickets were sold.
Explanation:
 We know that we can find the number of adult and student tickets sold, with this equation:
 

 Since 82 students attended, we can substitute 
 into the equation and solve for "a", in order to calculate the amount of adult tickets sold.
 into the equation and solve for "a", in order to calculate the amount of adult tickets sold.
 Then, "a" is:
 
