(a)
Step 1: Write out the formula
[tex]ra^{-m}=\frac{r}{a^m}[/tex][tex]\begin{gathered} \text{ Where} \\ a\text{ is a non-zero integer} \\ m,r\text{ are integers} \end{gathered}[/tex]
Step 2: Write out the given values and substitute them into the formula
[tex]\begin{gathered} \text{ In this case,} \\ r=5,a=k,m=3 \end{gathered}[/tex]
Therefore,
[tex]5k^{-3}=\frac{5}{k^3}[/tex]
(b)
Step 1: Write out the formula
[tex]\begin{gathered} \frac{a^m}{b^{-n}}=a^mb^n \\ \text{ Where} \\ b\text{ is a non-zero integer} \\ a,m,n\text{ are integers} \end{gathered}[/tex]
Step 2: Write out the given values and substitute them into the formula
[tex]a=x,b=y,m=4,n=6[/tex]
Therefore,
[tex]\frac{x^4}{y^{-6}}=x^4y^6[/tex]
