21. Which equations system has no solution?

$$\begin{array}{lcl} Which\;of\;the\;following\;systems\;of\;equations\;\\ does\;NOT\;have\;a\;solution?\\ \\ (F)\;2x+4y=8,\;x-y=0\\ (G)\;2x-4y=6,\;x-2y=3\\ (H)\;2x+4y=6,\;x-2y=3\\ (J)\;2x+4y=8,\;x+y=0\\ (K)\;2x+4y=8,\;x-2y=3\\ \end{array}$$