Thcorrdinates of the center of the circle, (h,k)=(x,8).
The radius of the circle, r=17.
The coordinates of a point on the circle, (xo,yo)=(3,-7).
The general equation of a circle is,

Now, put the values in the above equation to find x.
![\begin{gathered} (3-x)^2+(-7-8)^2=17^2 \\ (3-x)^2+15^2=289 \\ (3-x)^2+225=289 \\ (3-x)^2=289-225 \\ (3-x)^2=64 \\ 3-x=\sqrt[]{64} \\ 3-x=\pm8 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/hcatu6c4ohv1iah1koa50ckl32h81571ce.png)
Hence,

Hence, x=-5 or 11. Since it is given that x>0, the value of x is 11.