Let the number of tickets of Rs 5 bought = x
Let the number of tickets of Rs 10 bought = y.
Therefore, the total amount paid = 5x + 10 y = 150 (given)
Total number of tickets = x + y = 18 (given) → y = 18 - x
Substituting for y in first equation,
5x + 10(18 - x) = 150
5x + 180 - 10x = 150
180 - 150 = 10x - 5x = 5x
30 = 5x or x=305 = 6 and y = 18 - 6 = 12.
Hence, he purchased 6 Nos Rs 5 tickets and 12 Nos Rs 10 tickets