Question

C = 2 π r solve for r

Answer 1

C=2 πr
2 πr=C
r=C/2 π
The answer is r=C/2 π

Answer 2

C = 2πr
c/2π = 2πr/2π <--divide both sides by 2π
c/2π = r
r = c/2π <-- answer :)