Answer:
4.7
Explanation:
The segment marked x connects the midpoints of the chord and the diameter, so is the unknown leg of a right triangle with hypotenuse 16/2=8 and leg 6.5.
The Pythagorean theorem tells you ...
x² + 6.5² = 8²
x = √(64 -42.25) ≈ 4.664 ≈ 4.7