The standard circle equation is:
(x-h)^2+(y-k)^2=r^2, where (h,k) is the center of the circle and r is the radius.
We are given the radius is 15 and the center is (-3,5) so we simply need to plug in these values of the general case:
(x--3)^2+(y-5)^2=15^2
(x+3)^2+(y-5)^2=225