Well first you times the 0.3 to w and 10 which will give you 0.3w + 3 = 1.8w and subtracting 1.8 from 0.3 gives you
1.5w=3 and that is divided to w=2
The general equation for any circle with its center at point (a, b) is
(x - a)² + (y - b)² = (radius)²
So the circle in the question is centered at (-3, -4), and its radius is 3 .