A school play sold 120 tickets for ₹8,100. Adult tickets cost ₹80 and child tickets ₹50. How many child tickets were sold?

Explanation

1. 01

   Let $a$ adult tickets be sold, so $120 - a$ child tickets.

2. 02

   $80a + 50(120 - a) = 8100$, so $30a + 6000 = 8100$ and $a = 70$.

3. 03

   Child tickets $= 120 - 70 = 50$.