There are 400 balcony seats in the concert hall.
<u>Step-by-step explanation</u>:
Step 1 :
- The number of lower seats = 450 seats
Total seats = Lower seats + balcony seats
Step 2 :
- Tickets sold = 170 tickets
- Total tickets = x
Tickets sold = 1/5 of total tickets.
⇒ 170 = (1/5)x
⇒ x = 5170
⇒ x = 850 tickets
∴ Total seats in the concert hall is 850.
Step 3 :
Total seats = 450 + balcony seats
850 - 450 = balcony seats
∴ balcony seats = 400