## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$x=6, y =2 \text{ or }(6, 2)$
The system of equations is given by the following two equations: \begin{cases} x+y=8 \hspace{20pt} (1)\3mm] x-y=4 \hspace{20pt} (2) \end{cases} \text{The coefficients of y in the two equations are additive inverses.} \text{Therefore, we add the two equations to eliminate y} \[ \begin{aligned} &x+y =8\\[2mm] &x-y=4 \\[3mm] \hline & 2x=12 \\[2mm] &x =6 \end{aligned} \text{Substituting in equation (1) for } x=66+y=8 \\[3mm]y=8-6 \\[3mm] y = 2 Therefore, the solution is: $\boxed{x=6 \hspace{20pt} y =2 \hspace{20pt} \text{ or }\hspace{20pt} (6, 2)}$