Math question help help! quick

Iam in need of a tutor for my son in the northern ky area. can anybody me out

Pls me this is due today and i need i will make brainliest if you me answer correctly and i will report if you try to give me a dumb answer.

Given a circle with measures of (c, d, and r) and a circle with measures of (c', d', and r'), what is d if c c' = 12 and d' = 0.50? a) 3 b) 6 c) 12 d) 24