Answer:
See below
Explanation:
The solution will show the NUMBER Of adult and the NUMBER of child tickets purchased .
a = adult tickets cost = 15 a
c = children's tickets <=== this is equal to 20 - a
cost for children's tickets equals 10(20 - a)
15 a + 10c = 225 rememeber c = 20 -a <===put that in
15 a + 10 ( 20 -a) = 225 solve for a
15a + 200 - 10 a = 225
5 a = 25
a = 5 tix then c = 20 - a = 15 tix