Answer: 
Work Shown:
Note that (h,k) = (2,-3) is the center and r = 6 is the radius. The last line is not expanded out using the FOIL rule because its common practice to leave it in 
form. This form allows the reader to quickly determine the center and radius (rather than have to do a lot of algebraic steps before hand).
Definition of an exterior angle
At each vertex of a triangle, an exterior angle of the triangle may be formed by extending ONE SIDE of the triangle. See picture below.
Calculating the Angles
We can use equations to represent the measures of the angles described above. One equation might tell us the sum of the angles of the triangle. For example,
x + y + z = 180
2x + 2(5+x)=10
2x+10+2x=10
4x+10=10
4x=0
X=0
