First you gotta remember the equation:
[tex]Area = \pi {r}^{2} [/tex]
And also this equation to find r:
[tex]circumfrnce = 2\pi{r}[/tex]
To find r, let's plug in whatever we know about the circumference!
[tex]12\pi = 2\pi{r}[/tex]
We will find that r = 6. Now we can plug this into the 1st equation to find the area!
[tex]A = \pi {(6)}^{2} = 36\pi[/tex]
