C-Child ticket
4C-Adult tickets
6.10C+9.90(4C)=1188.20
6.10C+39.60C=1188.20
45.70C=1188.20
Divide both sides by 45.70 to get C.
C=26
This means 26 child tickets were sold that day.
Let's check our answer:
26×6.10=158.60
26×4=104 (Adult tickets)
104×9.90=1029.60
158.60+1029.60=1188.20
Therefore, 26 child tickets were sold on Friday.