Question

write 16^(-3/4) in radical notation

Answer 1

the numerator is the power, the denominator is the root, and the minus sign means take the reciprocal
you get
\[\frac{1}{\sqrt[4]{16^3}}\] as a first step

Answer 2

then the fourth root of 16 is 2, since \(2^2=16\) and \(2^3=8\) your "final answer" is
\[\frac{1}{8}\]