How many child tickets were sold

Question

At the movie theater, Child admission is $6.10 and adult admission is $9.30. On Thursday, 133 tickets were sold for a total sales of 993.70. How many child tickets were sold that day?

Answer 1

6.1*C + 9.3*A = 993.70

C+A = 133 ---> A = 133 - C

6.1*C + 9.3 ( 133 - C) = 993.7

61C + 93*133 - 93C = 9937

12369 - 32C = 9937

-32C = -2432

C=76 ---> A = 57