Verified answer

[tex]\displaystyle \left \{ {{x+y=4} \atop {3x+y=6}} \right. \\\\\left \{ {{y=4-x} \atop {3x+y=6}} \right. \\\\3x+4-x=6\\x=1\\y=4-1\\y=3\\(x,y)=(1,3)[/tex]

Ответ:

х=4-у

3(4-у)+у=6

12-3у+у=6

6=2у

у=3

х=1

3+1=4

3+3=6