First of all do you have NO idea how to work it out - I have no idea if you cannot do any of these problems or just some of them!?!
The first one is fairly tough and one of the best ways is to work it would be - write down your answer, then run it and print out the value at each point - it will teach you how Java works. Java is a bit confusing sometimes with problems like that.
The second one is fairllllly simple - is that the only code it gives?! If it was coded sensibly from the Boat object side of things I would expect lines:
The first 2 would give compile errors - wrong object type or something similar - its kind of like saying :
String myStr = 2;
because 2 is not a valid string object.
The last line s2=b would require a cast I think, but may work, again depends on compiler + best way is to just try!