\(\left\{{}\begin{matrix}\left(x+y\right)^2-4\left(x+y\right)=12\\\left(x-y\right)^2-2\left(x-y\right)=3\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\left(x+y\right)^2-4\left(x+y\right)-12=0\\\left(x-y\right)^2-2\left(x-y\right)-3=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\left(x+y-6\right)\left(x+y+2\right)=0\\\left(x-y-3\right)\left(x-y+1\right)=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\left(x+y\right)\in\left\{6;-2\right\}\\\left(x-y\right)\in\left\{3;-1\right\}\end{matrix}\right.\)
=>\(\left(x+y;x-y\right)\in\left\{\left(6;3\right);\left(6;-1\right);\left(-2;3\right);\left(-2;-1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(4,5;1,5\right);\left(2,5;3,5\right);\left(0,5;-2,5\right);\left(-1,5;-0,5\right)\right\}\)
