how to salve this differential?

In Maxima, you'd express this problem as:

          ex: 'diff(y,x)=y/(x-y) $
          sol: ode2(ex,y,x);

which yields the result

         (y*log(y)+x)/y = %c

solving for x:

solve(sol,x) => [x = %c*y-y*log(y)].

            -s