[tex]\displaystyle\bf\\2x + 3y + 4z = 13~~~\Big|~\cdot 2\\7x + 5y + 3z = 18\\.........\\4x + 6y + 8z = 26\\7x + 5y + 3z = 18\\................................~~~Adunam\\11x+11y+11z=44~~~\Big|~: 11\\\\x+y+z=4~~~(Suma~celor~3~numere)\\\\Triplul~sumei~celor~3~numere~este:\\\\3(x+y+z)=3\cdot4\\\\\boxed{\bf3(x+y+z)=12}[/tex]
