Considering a combination of functions I am sorry for the vague title - its because I don't know what I am talking about.
I have a function whose value is determined by considering the outputs of some other functions. For example,
F(x) = G(a,b) and H(x) and T(y)


*

*As you can see, I am not sure how to write the "and" part. That is, I want to say: In order to calculate F(x), you first have to calculate G(a,b) and H(x) and T(y); and then "mix them up in a certain way".

*How can I represent this idea mathematically? Can somone please point me to some resources that further explain this in baby-steps?


Followup:
Thank you for all your replies. Let me clarify what I want to do.
Consider a scenario where I want to find the value of a car. This depends on factors such as mileage, model, number of accidents, and also owner-bias. The owner-bias itself is a function of gender, years of driving experience, and age
So.. how can I come up with a symbolic way to represent this AND also define the interralations between all these factors?
I am sorry for the newbie question, please feel free to direct me to the relevant literature/terminology

The issue appears to be one of "dummy variables" and maybe composition of functions.  When you write, for example, q(x)=x^2, it really doesn't matter that the variable is x.  You also have that q(y)=y^2 and the same for any variable you name.  But we expect the same variables on both sides of the equation.  If we could show F(x)=G(a,b) that would say that F(x) doesn't depend upon a and b, so F(x) and hence G(a,b) must be constant.  If F really depends upon G(a,b), H(x), and T(y) we would expect to see F(a,b,x,y)= some expression involving G(a,b), H(x), and T(y).  An example would be F(a,b,x,y)=G(a,b)*H(x)+T(y).  Sometimes H(x) and T(y) are the inputs to G.  That we would write F(x,y)=G(H(x),T(y))
Qiaochu Yuan and I are trying to get at the same thing using different language.  I hope at least one is helpful.
