It seems you're working with an expression:

$\frac{3x}{x - 3}$

This expression is a rational function, meaning it is a fraction where both the numerator and denominator are polynomials. Let's break it down:

1. Numerator: $3x$
2. Denominator: $x - 3$

Important notes:

• This expression is undefined if $x = 3$, since the denominator would become zero, leading to division by zero.
• For any other values of $x$, the expression simplifies as it is.

So, the expression remains:

$\frac{3x}{x - 3}, \quad \text{with } x \neq 3.$

Would you like more details on how to work with this expression, or do you have any specific questions?

Here are 5 related questions:

1. What happens when you substitute specific values of $x$ into this expression?
2. How do you graph a rational function like $\frac{3x}{x-3}$?
3. Can you simplify the expression further under certain conditions?
4. What is the domain of the function $\frac{3x}{x - 3}$?
5. How does the function behave as $x$ approaches 3 from either side?

Tip: Always check for points where the denominator becomes zero when working with rational expressions!