What are the coordinates of vertex B' if the figure is rotated 90° counterclockwise about the origin?

B'(-5,2)

Step-by-step explanation:

Rotations

When rotating a point B(x,y) 90 degrees counterclockwise about the origin it maps to an image point B'(-y,x).

The image shows a figure formed by points ABCD. The coordinates of B are B(2,5).

This point will be rotated 90 degrees counterclockwise about the origin, thus the coordinates of the image point B' are B'(-5,2).

B'(-5,2)