Question

I was wondering how to do this.

Answer 1

$\bf \cfrac{3}{k}=-\cfrac{8}{k+8}\implies \cfrac{3}{k}=\cfrac{-8}{k+8}\implies \stackrel{cross-multiplying}{3(k+8)=-8(k)}\implies 3k+24=-8k \\\\\\ 11k=-24\implies k=-\cfrac{24}{11}$