Well, first I'm going to begin with converting #-.125# into a fraction.

Our first step is to change #-.125# into #-125/1000#. From there, we just simplify it.

#-125/1000# divided by #5# gives us #-25/200#. Divide by #5# again and we have #-5/40#. Once more, and we arrive at #-1/8#, which cannot be simplified further.

The next aspect of the question is to change #-.125# into a percentage. Well, the conversion for that is quite simple. Take the value and multiply it by #100#. That moves the decimal point up two units, and gives you a percentage. For us, #-.125# becomes #-12.5%#.