let f (x) =x (is under square root_)
g(x)=2x-1
h(x)=x^2

question is
(h.g.f) (9)

Is that what you mean:


f(x) = \sqrt x\\
g(x) = 2x-1\\
h(x) = x^2\\


Evaluate h(g(f(9)))

What you do is start with the inner-most function and evaluate it, then substitute its value into the next higher-level function, and so on. So here, you have:

Step 1: f(9) = \sqrt 9 = 3
Step 2: g(f(9)) = g(3) = 5
Step 3: h(g(f(9))) = h(5)= ??

I'm sure you can take it from here.