Odpowiedź:
x - Krystian
y - Artur
[tex]\left \{ {x+{y=25} \atop {2y+y=15}} \right. \\\left \{ {x+{y=25} \atop {3y=15 /:3}} \right. \\\left \{ {x+{y=25} \atop {y=5}} \right. \\\left \{ {x+{5=25} \atop {y=5}} \right. \\\left \{ {x=25-5} \atop {y=5}} \right. \\\left \{ {x=20\5} \atop {y=5}} \right.[/tex]
