Equation of a circle: (y-5k)² + (x-h)² = R² , where h & k are k are the coordinates of the center of the circle:
So the equation is (y-5)² + (x+3)² = 7² (49).
Now if the inner circle has a radius = R₁, its equation becomes
(y-5)² + (x+3)² = R₁². As you notice nothing changed but the radius value