Question

X+2y= -19
3x-y=20

Substituição

Answer 1

{x+2y= -19
{3x-y=20

y=3x-20

x+2*(3x-20)=-19
x+6x-40=-19
7x=-19+40
x=21/7
x=3

y=3x-20
y=3*3-20
y=9-20
y=-11