One way of simplifying the given expression is by using the following definition:
[tex]k^{-1}=\frac{1}{k}[/tex]So, for the given expression, we have:
[tex]-3k^{-1}=-3\cdot\frac{1}{k}=-\frac{3}{k}[/tex]Therefore, a possible answer is:
[tex]-\frac{3}{k}[/tex]