Вопрос в картинках...

1) $\left \{ {{x=3-2y} \atop {3^{x-y} =81}} \right.$
$\left \{ {{x=3-2y} \atop {3^{3-2y-y} =81}} \right.$
$\left \{ {{x=3-2y} \atop {3^{3-3y}=3^{4}}} \right.$
$3-3y=4$
$-3y=4-3$
$y=- \frac{1}{3}$
$x=3-2y=3- \frac{2}{3}=\frac{7}{3}=2\frac{1}{3}$

Ответ: $(2\frac{1}{3};-\frac{1}{3})$

2) $\left \{ {{2^{2x+y}=2^{5}} \atop {8x+1=3y}} \right.$
$\left \{ {{2x+y=5} \atop {8x+1=3y}} \right.$
$\left \{ {{y=5-2x} \atop {8x+1=3(5-2x)}} \right.$
$8x+1=15-6x$
$14x=14$
$x=1$
$y=5-2x=5-2=3$

Ответ: (1; 3)

3) $\left \{ {{3^{3x-2y}=3^{4}} \atop {3^{6x+y}=3^{3}} \right.$
$\left \{ {{3x-2y=4} \atop {6x+y=3} \right.$
$\left \{ {{3x-2(3-6x)=4} \atop {y=3-6x} \right.$
$3x-6+12x=4$
$15x=10$
$x= \frac{2}{3}$
$y=3-6x=3-\frac{2*6}{3}=3-4=-1$

Ответ: $(\frac{2}{3};-1)$