9. As shown in the figure, the four vertices of square $A B C D$ are on the graphs of the inverse proportion functions $y=\frac{12}{x}$ and $y=\frac{20}{x}$ in the first quadrant, with the diagonals of the square parallel to the $x$-axis and $y$-axis, respectively. Then the x-coordinate of point $B$ is
$4$