Answer:
D. 5
Explanation:
We can triangle JHK is isosceles because two of its sides are radii, and radii of the same circle are always equal. Let the radius equal r. We can say that both JH and HK equal r because the extend from the center to the circle. We can set up the equation:
PJHK = JK + JH + HK
18 = 8 + r + r
10 = 2r
r = 5
Since HK equals r, it equals 5.