Respuesta: a) (x, y) = (7, -5)
Explicación paso a paso:
[tex]\left \{ {{y=2-x} \atop {y+2x=9}} \right.[/tex]
2-x+2x=9
x=7
y= 2-7
y= -5
(x, y)=(7, -5)
[tex]\left \{ {{7+(-5)=2} \atop {-5+2.7=9}} \right.[/tex]
[tex]\left \{ {{2=2} \atop {9=9}} \right.[/tex]
(x, y) = (7, -5)
