[tex] \left \{ {{x+y=10} \atop {x-y=2}} \right. \Leftrightarrow \left \{ {{x=10-y} \atop {10-y-y=2}} \right. \Leftrightarrow \left \{ {{x=10-y} \atop {2*y=8}} \right. \Leftrightarrow \left \{ {{x=10-y} \atop {y=4}} \right. \Leftrightarrow \left \{ {{x=6} \atop {y=4}} \right.[/tex]
