To rotate a point \( (x, y) \) by \( 180^\circ \) clockwise around the origin, you can use the following transformation:
\[ (x, y) \to (-x, -y) \]
For point \( B(5, -9) \):
- \( x = 5 \) becomes \( -5 \)
- \( y = -9 \) becomes \( 9 \)
Thus, the coordinates of point \( B' \) after the \( 180^\circ \) clockwise rotation around the origin are:
\[ B'(-5, 9) \]
So, the coordinates of point \( B' \) are \( (-5, 9) \).