Answer:
17.872, 8
Explanation:
Chords that pass through the center are the diameter, and lines that are tangent to the circle are perpendicular to the diameter at that point.
Therefore, what we are looking at are right triangles, and we can find the distance using Pythagorean theorem.
c² = a² + b²
(19.5)² = (7.8)² + b²
b ≈ 17.872
c² = a² + b²
(10)² = (6)² + b²
b = 8