To all who are confused - so sorry. My bad, I think that I lost one of my photos during the computer crash. Let's tried to do this -
Using A and B you will be making twelve 1/2 sq triangle blocks that measure 3-1/2" square when sewn, cut and pressed, as in the diagram I drew, and trimmed to 3-1/2" if needed.
Then using B and C you will be making the triangles that you will finish next week. This step is shown in the second and third photos.