[tex]\left\{\begin{array}{ccc}2x-y=5\\2x-2y=4&|\cdot(-1)\end{array}\right\\\underline{-\left\{\begin{array}{ccc}2x-y=5\\-2x+2y=-4\end{array}\right}\ \ \ \ |add\ both\ sides\\.\ \ \ \ \ \ \ \ y=1\\\\substitute\ the\ value\ of\ y\ to\ first\ equation\\\\2x-1=5\ \ \ |+1\\2x=6\ \ \ |:2\\x=3\\\\\left\{\begin{array}{ccc}x=3\\y=1\end{array}\right[/tex]
