Answer:
102 adults, 165 children
Explanation:
Let a be the number of adults, and let c be the number of children. We set up and solve this system of equations:
a + c = 267---------> 7a + 7c = 1869
12a + 7c = 2379------->12a + 7c = 2379
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5a = 510
a = 102, c = 165