Answer :

[tex]C=\frac{1}{8}*R*t \\\\ C=\frac{Rt}{8} \\\\ \boxed{R=\frac{8C}{t}}[/tex]
C=[tex] \frac{1}{8} [/tex]Rt=[tex] \frac{Rt}{8} [/tex]

Multiply both sides by 8.
8C=Rt

Divide both sides by t.
[tex] \frac{8C}{t} [/tex]=R