Answer
$17$
Work Step by Step
Pythagorean Theorem says that for a right triangle (if $z$ is the hypotenuse and $x,y$ are the other sides): $x^2+y^2=z^2$.
Hence here: $8^2+15^2=h^2\\64+225=h^2\\289=h^2\\h=\pm17$
But the hypotenuse must be positive, so it is $17$.
