A bus is carrying 12 passengers with some people having ₹8 tickets and the remaining having ₹9 tickets. If the total money received from these passengers is ₹100, find the number of passengers with each type of tickets.

Let the number of passengers having ₹8 tickets be y. Then, the number of passengers with 
₹9 tickets is (12−y). 
Total money received from the passengers = ₹100

So, according to the question :

8y + (12 - y)9 = 100
8y + 108 – 9y = 100
y = 8
Number of passengers having ₹8 tickets be 8. 
Then, the number of passengers with ₹9 tickets is (12−8) = 4.