Simplify the following expression. Assume variables are positive. Express your answer using rational exponents.

Let's simplify the expression:
[tex]\begin{gathered} (x^{-\frac{1}{2}}\cdot y^{-\frac{2}{3}}\cdot z^{-2})^{-\frac{1}{2}}=x^{(-\frac{1}{2})(-\frac{1}{2})}y^{(-\frac{2}{3})(-\frac{1}{2})}z^{(-2)(-\frac{1}{2})} \\ =x^{\frac{1}{4}}y^{\frac{1}{3}}z \end{gathered}[/tex]Therefore the answer is:
[tex]x^{\frac{1}{4}}y^{\frac{1}{3}}z[/tex]