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

Well, if that's how you calculate $F(x)$, then it's not just a function of $x$, is it?  You should write it as $F(G(a, b), H(x), T(y))$.  Unless you're saying that $a, b, y$ are all themselves functions of $x$, in which case I guess you should write
$$F(x) = S(G(a, b), H(x), T(y)).$$
