$2 \times ( + 1) + 2 \times x + 7 \times ( - 2) = 0$
$ + 2 + 2x - 14 = $$2x = 14 - 2 = 12$
$x = \frac{{12}}{2} = + 6\,\,{\rm{for}}\,\,S$
${K_4}\mathop {Fe}\limits^{ * \,\,} {(CN)_6}$
$4 \times ( + 1)\,x + 6 \times ( - 1) = $$4 + x - 6 = 0$
$x = 6 - 4 = + 2\,\,{\rm{for}}\,\,Fe$.