Question

Помогите!!! Пожалуйста!! Очень надо!!!

Answer 1

$\displaystyle\bf\\1)\\\\\left \{ {{5x-y=1} \atop {x+2y=20}} \right. \\\\\\\left \{ {{y=5x-1} \atop {x+2\cdot(5x-1)=20}} \right. \\\\\\\left \{ {{y=5x-1} \atop {x+10x-2=20}} \right. \\\\\\\left \{ {{y=5x-1} \atop {11x=22}} \right. \\\\\\\left \{ {{x=2} \atop {y=5\cdot 2-1}} \right. \\\\\\\left \{ {{x=2} \atop {y=9}} \right. \\\\\\Otvet \ : \ (2 \ ; \ 9)$

$\displaystyle\bf\\2)\\\\+\left \{ {{x+3y=7} \atop {2x-3y=-4}} \right. \\----------\\3x=3\\\\\boxed{x=1}\\\\3y=7-x=7-1=6\\\\y=6:3\\\\\boxed{y=2}\\\\\\Otvet \ : \ (1 \ ; \ 2)$