square root of X^8 over 81Y^7

Is that \sqrt{\frac{x^{8}}{81y^{7}}} or \frac{\sqrt{x^{8}}}{81y^{7}}?

I assume the former?

Then, use the exponent laws. Remember, the exponents of exponents multiply.

\left(\frac{x^{8}}{81y^{7}}\right)^{\frac{1}{2}}

8 times 1/2 is 4, so we have in the numerator: x^{4}

In the denominator, what's the square root of 81? What is 7 times 1/2?

Can you get it now?