Answer:
140 child tickets were sold
Explanation:
a = number of adult tickets
c = number of child tickets
a+c = 350
6.50 c + 8.50a = 2695
Multiply the first equation by -8.50 together
-8.50c -8.50c =-2975
Add this to the second equation to eliminate a
-8.50c -8.50c =-2975
6.50 c + 8.50a = 2695
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-2c + 0a = -280
Divide by -2
-2c/-2 = -280/-2
c = 140