We know that the equation of circle is

$$(x-h{)}^2+(y-k{)}^2=r^2$$

Given that,

$$(h,k)=(8,5),r=9$$

Then by plugging in the values, we have:

$$(x-8{)}^2+(y-5{)}^2=9^2$$

$$(x-8{)}^2+(y-5{)}^2=81$$