The expression you’ve written, $^{3\sqrt{x^{18}y^6}}$, appears to be incomplete or incorrectly formatted, so I need to clarify what you're aiming to represent. Based on common mathematical notations, I think you might be referring to either:

1. A radical expression involving a square root or cube root, such as $3\sqrt{x^{18} y^6}$.
2. An exponentiation where the whole expression is raised to the power of 3 or a root like $(x^{18} y^6)^{3}$.

Could you clarify if you mean:

• The cube root of $x^{18} y^6$, i.e., $\sqrt[3]{x^{18} y^6}$?
• Or something else?

If it's the cube root, we can simplify it step by step. Let me know!