Looking at the given circle, the diatance from the center to the circumference is 5. This means that the radius of the circle is 5. The radius of the circle is always the same. The line at the base of the circle that touches the circimference is a tangent. The line from the center of the circle to this tangent is also a radius and it forms 90 degrees with the tangent. Thus, the right angle triangle formed is shown below
To find x, we would apply pythagorean theorem which is expressed as
hypotenuse^2 = longer leg^2 + shorter leg^2
From the triangle,
hypotenuse = 17
shorter leg = 5
longer leg = x
Thus, we have