Respuesta :

area=pi times r^2
circunference=2pi times r

circunference=18pi
18pi=2pi times r
divide both sides by 2
9pi=pi times r
divide both sides by pi
9=r

subsitute
area=pi times r^2
area=pi times 9^2
area=pi times 81
area=81pi

answer is area=81pi cm^2