Question

sistema  2x+y=4
             3x-y=1

Answer 1

$\left \{ {{2x+y=4} \atop {3x-y=1}} \right.$

Vamos fazer pela adição
cancela o y  e soma os membros

5x=5
x=5/5
x=1

se 3x-y=1
3.1 -y=1
3-y=1
-y=1-3
-y=-2
y=2

S={(1,2)}

Answer 2

$\left \{ {{2x+y=4}(*1) \atop {3x-y=1}} \right. \\\\ \left \{ {{2x+y=4} \atop {5x=5}} \right. \\\\ 5x = 5\\\\ \boxed{x=1}$

$2x+y = 4\\\\ 2(1)+y = 4\\\\ 2+y = 4\\\\ \boxed{y=2}\\\\\ \boxed{S(1,2)}$