Answer :
a + c = 181......a = 181 - c
9.3a + 5.8c = 1343.80
9.3(181 - c) + 5.8c = 1343.80
1683.3 - 9.3c + 5.8c = 1343.80
-9.3c + 5.8c = 1343.80 - 1683.3
- 3.5c = - 339.5
c = -339.5 / -3.5
c = 97 <== child ticket sold
9.3a + 5.8c = 1343.80
9.3(181 - c) + 5.8c = 1343.80
1683.3 - 9.3c + 5.8c = 1343.80
-9.3c + 5.8c = 1343.80 - 1683.3
- 3.5c = - 339.5
c = -339.5 / -3.5
c = 97 <== child ticket sold