Question

x-3y=1
3x+y=13
РОзвязать систему

Answer 1

x = 3y + 1
3(3y + 1) + y = 13

x = 3y + 1
9y + 3 + y = 13 *

*10y = 10
y = 1

x = 4 
y = 1 

Answer 2

$\left \{ {{x-3y=1} \atop {3x+y=13}} \right.$
$\left \{{{x=1+3y}\atop {3(1+3y)+y=13}} \right.$
$\left \{ {{x=1+3y} \atop {3+10y=13}} \right.$
$\left \{ {{x=1+3y} \atop {10y=10}} \right.$
$\left \{ {{x=1+3y} \atop {y=1}} \right.$
$x=1+3y=1+3*1=4$
Ответ: x=4; y=1