[tex]\displaystyle\bf\\\left \{ {{x-2y=5} \atop {x+y=4}} \right. \\\\\\\left \{ {{x=2y+5} \atop {2y+5+y=4}} \right. \\\\\\\left \{ {{x=2y+5} \atop {3y=4-5}} \right. \\\\\\\left \{ {{x=2y+5} \atop {3y=-1}} \right. \\\\\\\left \{ {{x=2\cdot\Big(-\dfrac{1}{3} } \Big)+5\atop {y=-\dfrac{1}{3} }} \right. \\\\\\\left \{ {{x=-\dfrac{2}{3} } +5\atop {y=-\dfrac{1}{3} }} \right. \\\\\\\left \{ {{x=4\dfrac{1}{3} \atop {y=-\dfrac{1}{3} }} \right.[/tex]

[tex]\displaystyle\bf\\Otvet \ : \ \Big(4\frac{1}{3} \ ; \ -\frac{1}{3} \Big)[/tex]