The equation of a circle:

(h, k) - center
r - radius
Look at the picture:
center: (4, -2) → h = 4, k = -2
radius: r= 5
Substitute:

Answer:
x = 20
Step-by-step explanation:
Exterior angles are equal.
7x - 3 = 6x + 17
Add 3 and subtract 6x to both sides.
x = 20 is the answer.