To find the answer, we canuse Pythgorus thereom.
As x is perpendicular to the chord(16), we can determined that x cut it's mid point, making the two sides of the chord eqaul, which means one side of the chord is:
16/2
=8
We can then find the radius that touch the chord from it's diameter, by dividing it by two as diameter = radius x 2:
20/2
=10
Then,from the triangle (see photo), we can calculate the value of x:
8^2 + x^2 = 10^2
64 + x^2 = 100
x^2 = 36
x = _/36
x = 6
Therefore, x=6 is the answer.
Hope it helps!