Question

I need help remembering the steps to solve

Answer 1

Take a common point ( C in this case)
1. Take the difference of the y coordinates from the point vertical to C.
   C from D in this case.
2.Take the diff of the x coordinates from the points  horizontal to the first.
  C from B in this case.
3. Now add the diff to the common point. X to x Y to y.
 

Answer 2

Picture is sloppy cant see it for real