Question

A triangle ABC with vertices A(6,8) B(6,12) C(10,12) is rotated to 180. What are the coordinates of B

Answer 1

Assuming rotation is about origin, then
R180:  (x,y)->(-x,-y)

So
A(6,8)->A'(-6,-8)
B(6,12)->B'(-6,-12)
C(10,12)->C'(-10,-12)