ALGEBRA HELP PLZZZZZZZZZ

Apply this transformation to a square with vertices A(3,-4) B(7,-4) C(3,-8) D(7,-8)

apply this (x,y) ----> (-x,y)


I need to rotate this 180 degrees from the origin How do I do this?  DO I use the corrdinates from the prior answer and move it 180 degrees to a new quadrant? 

PLEASE HELP ME AND SHOW HOW TO DO THIS!! THANK YOU!!!!