A cinema sold 200 tickets for one show. Balcony tickets cost Rs 150 each and stall tickets Rs 100 each, and the total collection was Rs 26000. How many balcony tickets were sold?

Let $x$ balcony and $y$ stall tickets be sold. $x+y=200$ and $150x+100y=26000$. Substituting $y=200-x:150x+20000-100x=26000$, so $50x=6000$ and $x=120$, giving $y=80$. Check: 120 + 80 = 200 and 18000 + 8000 = 26000. 80 is the number of stall tickets, the swapped unknown; 104 comes from dividing Rs 26000 by Rs 250, as if tickets were sold only in pairs; 130 is Rs 26000 divided by 200, which is the average price per ticket, not a count.