[tex] \frac{x {}^{ - 1}y {}^{ - 2} }{z {}^{ - 3} } [/tex]
if the upper number got power of negative it will go down and the down will go up
So that,
[tex] \frac{z {}^{3} }{x {}^{1} {y}^{2} } [/tex]
power of 1 can no need to write
Negative exponents work like this:
[tex] a^{-m} = \dfrac{1}{a^m} [/tex]
So, a number raised to a negative power simply means the multiplicative inverse of that number raised to the positive power.
So, in your case, you have
[tex] \dfrac{x^{-1}y^{-2}}{z^{-3}} = \dfrac{\frac{1}{x}\frac{1}{y^2}}{\frac{1}{z^3}} [/tex]
We can rework this expression to get
[tex] \dfrac{z^3}{xy^2} [/tex]
