Chapter 7 - Section 7.1 - Systems of Linear Equations in Two Variables - Exercise Set - Page 818: 20

The required value is $x=2,\,y=4$

By adding both equations, we obtain: $\begin{align} & x+y+\left( x-y \right)=6-2 \\ & 2x=4 \\ & x=2 \end{align}$ Substitute the value of $x=2$ in the second equation and obtain, $\begin{align} & 2-y=-2 \\ & -y=-2-2 \\ & -y=-4 \\ & y=4 \end{align}$ Thus, the value of $x=2$ and $y=4$.