Question 937688
Your "middle step" should be expressed as this:


{{{(x(1-y)-y(1-x))/((1-x)(1-y))}}}


PERFORM THE INDICATED OPERATIONS and simplifications for the numerator!  Just that  first part-step will first become this:


{{{(x-xy-y+xy)/((1-x)(1-y))}}}


Keep going and finish.