X is chillin'

Overheard during a free period I have...

I am sitting at my desk doing work in my room, next to another teacher who teaches in my room during my free period. He is giving a math test to his class. A student comes up to ask him a question. They are talking...

Teacher: "Well, before you do anything else, you have to get x by itself."
Student: "Ok..."

[uncomfortable pause]

Teacher: "You're not sure how to get x by itself?"
Student: "No."
Teacher: "Ok, well, what is x doing right now?"
[pause]
Student: "Chillin."
Teacher (laughing) "Ok, well, it's chillin' now with what kind of sign attached to it?"

... and the conversation continued.

However, in ten years of teaching math I'd never thought of a variable as chillin'. I guess I could see the student's point. X, indeed, at the moment wasn't doing anything - just chillin'.