Answer:
x = 6.8
Explanation:
The angle where the tangent meets the diameter is a right angle. This means the triangle is a right triangle and the Pythagorean theorem applies.
x² = 3.2² +6² . . . . . . . . the radius is 3, so the diameter is 6
x² = 46.24
x = √46.24 = 6.8
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Additional comment
This is an 8-15-17 right triangle, scaled by a factor of 0.4.