Answer:
The answer is x=12
Explanation:
In order to determine the "x" value, we have to know about the tangent to a circle.
The line that joins two infinitely close points from a point on the circle is a Tangent. It means, the lines that intersect the circles exactly in one single point are tangents.
I have attached an image that shows a tangent to a circle. Also there is a formula that relates the segments of the circle.
According to the same notation of the image:

In this case:

Finally the answer is x=12