Помогите пожалуйста решить[latex] \left \{ {{x+2y=3} \atop {3 x^{x+y}=81 }} \right. [/latex]

[latex] \left \{ {{x+2y=3} \atop {3^{x-y} =81}} \right. [/latex] [latex] \left \{ {{x=3-2y} \atop {3^{x-y} =81}} \right.[/latex] [latex] \left \{ {{x=3-2y} \atop {3^{3-2y-y} =81}} \right.[/latex] [latex] \left \{ {{x=3-2y} \atop {3^{3-3y}=3^{4}}} \right.[/latex] [latex]3-3y=4[/latex] [latex]-3y=4-3[/latex] [latex]y=- \frac{1}{3}[/latex] [latex]x=3-2y=3- \frac{2}{3}=\frac{7}{3}=2\frac{1}{3}[/latex]