You have a triangle with the following vertices:
F(6,3), G(3,4),H (1,7)
If the triangle is rotated by 180°, then the new vertices points are located at the following points:
F(6,3) -> F'(-6,-3)
G(3,4) -> G'(-3,-4)
H (1,7) -> H'(-1,-7)
That is, the coefficients of each coordinate are the same but with opposite signs.