40) This is a single compound. You can see this by rotating either structure by 180°.
42) This looks to me like a single compound
47) Try imagining (I) from the other side of the viewing plane. Does it look like (II). It's tempting to assume that since both dashes/wedges changed that these are diastereomers, but in fact you are just changing you viewing angle.
55) This is a monosubstituted ring, and any way you draw 1-bromocyclohexane it will always be the same compound, because it is achiral. Also, ring flips are a conformational change and only alter the equitorial-axial position of substitutents and does not change the absolute stereochemistry.
These kinds of questions are much easier to answer with models.