HELP ASAP i dont know how to do any of this

Answer:
Step-by-step explanation:
Circumference is= to diameter * Pi
[tex]6\pi = 6*3.14=18.84\\15\pi=15*3.14=47.1[/tex]
For the ones that are radius, double it, then pi
[tex]21*2\pi = 42\pi =42*3.14=131.88\\6.7*2\pi=13.4\pi =13.4*3.14=47.076[/tex]