B) is your answer
The cost for x children is $6. This means that the children is a variable (x), but no matter how much children there is, each ticket costs $6 (constant). (becomes 6x)
The cost for y adult is $11. This means that the adults is a variable (y), but no matter how much adult there is, each ticket costs $11 (constant)
(becomes 11y)
So B) is correct.
hope this helps
