c is good. You get take a triple from 180 degrees most easily by just changing the sign of the first element.
Actually I forgot that triple subtraction comes up later in the book (in VMTTC we come to it in lesson 34), so my advice was not the best. I should have said to drop a perpendicular from M onto AB, call that point P. Then angle PMA is clearly 5,4,- and the required angle is double that.
For d I’m not sure of your method, though your answer is right.
My advice would be to draw DB, then you can take 4,2,- from 1,1,- (the triple for 45 degrees), and then double.