x+2y=4

x + 2y = 4

2x - y = 13

$\small{ \begin{array}{lrcl} (1) & x+2y &=& 4 \\ & x &=& 4 - 2y \\\\ (2) & 2x-y &=& 13 \\ & 2(4-2y) -y &=& 13 \\ & 8 -4y - y &=& 13 \\ & 8 - 5y &=& 13 \qquad | \qquad +5y-13\\ & 8-13 &=& 5y \\ & -5 &=& 5y \qquad | \qquad :5\\ & -1 & =& y\\ & \mathbf{y} &\mathbf{=}& \mathbf{-1}\\\\ & x &=& 4 - 2(-1) \\ & x &=& 4 + 2\\ & \mathbf{x} &\mathbf{=}& \mathbf{6} \end{array} }$