To calculate $f(g(3))$, we need more information about the functions $f(x)$ and $g(x)$.

If you provide the definitions of both $f(x)$ and $g(x)$, I can help you evaluate $f(g(3))$. Could you specify these functions?

Would you like to provide that detail or ask about related concepts? Here are some relative questions:

1. What types of functions are $f(x)$ and $g(x)$ typically?
2. How do you compose two functions like $f$ and $g$?
3. What is the difference between $f(g(x))$ and $g(f(x))$?
4. How does function composition apply in real-world problems?
5. Can you give examples of nested functions in algebra or calculus?

Tip: Always substitute the inner function result first when working with compositions.