Answer:
[tex]k=-\frac{a}{b}+ \frac{c}{b}[/tex]
Step-by-step explanation:
[tex]\frac{a}{k}+b = \frac{c}{k}\\\frac{a}{k}- \frac{c}{k} = -b\\\frac{1}{k}(a-c)=-b\\a-c=-bk\\k=-\frac{a}{b}+ \frac{c}{b}[/tex]