Answer: [tex]r = \frac{C}{2\pi }[/tex]
Step-by-step explanation:
Im assuming you mean [tex]C = 2\pi r[/tex].
To solve for r means that you have to isolate it like c is currently. To do this you would have to divide by whatever it's multiplied by (in this case 2pi).
If you divide both the right and left sides by this you get
[tex]r = \frac{C}{2\pi }[/tex]