Answer :
The pythagorean theorem establish that:
[tex]c^2=a^2+b^2[/tex]where c is the hypotenuse, a and b are the legs of the right triangle.
In this case then:
[tex]17^2=x^2+8^2[/tex]Solving for x we have:
[tex]\begin{gathered} x^2+8^2=17^2 \\ x^2=17^2-8^2 \\ x^2=225 \\ x=\sqrt[]{225} \\ x=15 \end{gathered}[/tex]Therefore, x=15.