Assume that the number of adult tickets is a and the number of child tickets is c.
We are given that the adult ticket is sold for 20$, the child ticket is sold for 10$ and that the total is $15,000. This means that:
20a + 10c = 15,000 ..........> equation I
We are also given that number of child tickets is 3 times that of adult's. This means that:
c = 3a .........> equation II
Substitute with equation II in equation I to get a as follows:
20a + 10c = 15,000
20a + 10(3a) = 15,000
20a + 30a = 15,000
50a = 15,000
a = 300 tickets
Substitute with the value of a in equation II to get c as follows:
c = 3a
c = 3(300)
c = 900 tickets
Based on the above calculations,
number of child tickets = 900 ticket
number of adult tickets = 300 ticket
