Three times as many childeren as adults attended a concert on Saturday. An adult ticket is $7 and a child's ticket is $3. The theater collected $6000. How many people bought tickets?

Let

a= adults
3a= children

7a + 3(3a) = $6000

16a = 6000
a = 6000/16 = 375
number of adult

Number of children
3a = 375*3 = 1125

1125 + 375
Number of people
1500