A positive minus a positive equals?

It depends, whether if the positive number you are adding is higher than your negative number that you started off with. (Eg. -2+3=1)

It depends once again, if the positive number you are subtracting is higher than the positive number that you starting off with, then yes. (Eg. 6 - 8 = -2)

Yes, if [x-(-y)=z] then it can be turned into [x+y=z] because the two negatives cancel each other out, causing you to be left with the opposite, a positive of plus sign.

Such a calculation always gives a negative answer.

Yes, the only time a quotient is negative is when a negative and a positive number are divided.