How to Calculate the value of gp_Pnt after Transform from old gp_Ax3 to new gp_Ax3?

Hi:
About the Coordinate Transformation(include translation/rotate/scale ect),if I have got the value of gp_Pnt in old gp_Ax3 already,then,after tranform to the new gp_Ax3 ,how to get the new value of this gp_Pnt in new gp_Ax3?I want to get the Relative coordinate in new gp_Ax3 not the Absolute coordinate.
Thanks
Jason.Jiang