Answer:
The balcony seat costs $9, the orchestra seat costs $9 + $6 = $15. 
Explanation:
Let x is the cost/price of one balcony seat, in dollars. 
 
Then the cost of one orchestra seat is (x+6) dollars, according to the condtion. 
 The total cost of tickets is 
 
250x + 400*(x+6) = 8250. 
Simplify it step by step. 
 
250x + 400x + 2400 = 8250, 
 
650x = 8250 - 2400 = 5850 ====> x = 5850/650 = 9. 
 
 
Answer. The balcony seat costs $9, the orchestra seat costs $9 + $6 = $15. 
 
 
Check. 9*250 + 15*400 = 8250. Correct.