Question

C= pi times d ; Solve for d

Answer 1

If:
\[
C=\pi d
\]Then:
\[
C\cdot\frac{1}{\pi}=\pi d\cdot\frac{1}{\pi}\implies\\
\frac{C}{\pi}=\frac{\pi d}{\pi}=1\cdot d=d\implies\\
\frac{C}{\pi}=d
\]

Answer 2

Okay , where did you get the 1 from ?