You have the following points that form a triangle in the coordinate system:
F(8,3)
G (3,5)
H (1,7)
If the traingle is rotated by 180° around the origin of coordinates you have:
F'(-8,-3)
G'(-3,-5)
H'(-1,-7)
without importance of the sense of the rotation, if it is 180°, each coordinate of each point will have the opposite sign bu the same coefficient.