1. The problem statement, all variables and given/known data Given y = xz5 and x = zg (where g is some constant) find : (∂y / ∂x)z 2. Relevant equations 3. The attempt at a solution I understand the concept of a partial derivative, but I've never seen one such that there is a variable held fixed, or one where ∂x is not changing independently. This is a statistical mechanics problem. Any tips on how to do this? My solution is basically treat z as a constant but that would be the same as taking the partial without holding z constant. I'm not sure what to do about x either. Just need an example of or instruction on how to do this. Thanks.