English Grammar
posted by John .
A: What time is your math/Math class?
B: At eleven fortyfive.
Do we have to use 'math' or 'Math'?
And is it a common noun or a proper noun?

You use "math" when you're making a general reference to the class, whether it's Algebra I or Geometry or whatever.
You use "Math" when it's part of the formal name of the course. "When I was a senior in high school, my math course was called Math IV." 
If "Math" is the specific title of that particular class, then use the capital. Otherwise the lower case is fine. However, specific titles typically include some numerical designation, such as "Math 101."
I hope this helps. Thanks for asking. 
2.4578*698

"math" and it is a common noun