Answer: 77 children tickets were sold that day
Explanation:
5.20x+9.50y=1255.40
x+y=167
5.20x+9.50(167-x)=1255.40
x+y=167 5.20x+1586.50-9.50x=1255.40
-x -x -4.30x+1586.50=1255.40
y=167-x -1586.50 -1586.50
-4.30x=-331.1
-4.30 -4.30
x=77
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