[tex] \underline{+\left\{\begin{array}{ccc}x+y=3\\x-y=1\end{array}\right}\ \ \ \ |\text{add both sides of the equations}\\\\.\ \ \ \ 2x=4\ \ \ \ |:2\\.\ \ \ \ x=2\\\\\text{put the value of x to the first equation}\\\\2+y=3\ \ \ \ |-2\\\\y=1\\\\Answer:\ x=2,\ y=1\to(2,\ 1) [/tex]
