Question

quanto e x+y=-1
x-y=3

Answer 1

x+y=-1
x-y=3
x=3+y
3+2y=-1
2y=-4
y=-2
x-(-2)=3
x+2=3
x=1
X=1; Y=-2

Answer 2

x + y = - 1; x - y = 3 (+); 2x = 2; X= 2/2; X = 1; x - y = 3; 1 - y = 3; 1 - 3 = y; - 2 = y; y = - 2; ( x = 1; y = - 2)