Answer:
x = 7.5
Step-by-step explanation:
If two scants are drawn from a point outside the circle then the product of one secant and its external segment is equal to the product of other secant and its external segment.
By applying this property in the picture attached,
OB × OA = OC × OD
(6 + 3)6 = (12 - x)12
54 = 144 - 12x
12x = 144 - 54
12x = 90
207
idek
This is more of a computer kind of thing, but try clicking the next thing at the bottom.
The two circles centered at point A are concentric and similar.