Hey Shirl,
It can be confusing at first, but you'll get the hang of it! You are calculating three results, but because your print statements are after the loop, you only see the result from the last calculation. You could have three separate result variables, or you you could print each result inside the loop, before you compute a new one.
As far as style goes, there's no reason to pass thirdSide into your hypoteneuse method. Use a local variable instead.
You should pass in the bothSides variable though. The hypoteneuse method uses that for its calculation, so it is better to have it as a parameter than a member variable. In fact, the best style would be to pass in the two values individually and let the hypoteneuse method do the full calculation, but I'm not sure what your assignment was.