Check if variable values belongs to which lists

What is the best way to check if a variable value is the same as which one in list 1 or list 2?
For example:
List 1 {2,4,6,9,11}
List 2 {5,7,8,10,12}
variable x=10

What should i do if i want to check that x is belong to list 2

You can use If-Else condition with operator “contains” for it.