Maths problem: I need help, I don't know how to determine constant or not constant, thanks.?

x,y,z are VARIABLES, 每一個會因其他兩個的"轉變"而"改變".
Given that: y α x, y α 1/√z 
Connecting the relationship of x,y,z, we have:
y = kx/√z,where k -- a constant(不會變的數字)

 　...^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^...
a) y/x = constant or not ?
===================
y = kx/√z
=> y/x = k/√z
y/x contains a variable z, ∴ it's a variable.
∴ y/x -- NOT a constant

b) y√z/x = constant or not ?
=================== =
y = kx/√z
=> y√z/x = k
y√z/x contains ONLY a CONSTANT k, but no variables.
∴ y√z/x -- a constant

c) x/y√z = constant or not ?
=================== =
y = kx/√z
=> 1/k = x/y√z
=>x/y√z = 1/k  
x/y√z contains ONLY a CONSTANT k, but no variables.
∴ x/y√z -- a constant

 　~~~~~~~~~~~~~ THE END ~~~~~~~~~~~~
☆☆ lf "..." contains NO VARIABLE, 
　　then "..." is a CONSTANT.