We know that the equation of circle is

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

Given that,

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

Then by plugging in the values, we have:

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

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