ANSWER:
15 units
STEP-BY-STEP EXPLANATION:
We can determine the BC value we can determine it by means of the Pythagorean theorem, with the hypotenuse 17 and the other side 8, therefore:
[tex]\begin{gathered} h^2=a^2+b^2 \\ \\ \text{ We replacing} \\ \\ 17^2=8^2+b^2 \\ \\ b^2=289-64 \\ \\ b=\sqrt{225} \\ \\ b=15 \end{gathered}[/tex]Therefore, the length of BC is 15 units.