The answer would be [tex] \frac{5d}{k} [/tex].
First, we have to flip the equation.
[tex] \frac{1}{5}fk = d [/tex]
Last, we divide both sides by k/5.
[tex] \frac{\frac{1}{5}fk}{\frac{k}{5}} = [/tex] [text] \frac{d}{\frac {k}{5}} [/tex]
Answer: f = [tex] \frac{5d}{k} [/tex]
