Question

{ x + y =5 x - y = - 5

Answer 1

x + y = 5
x - y = - 5       Some as duas equações

2x = 0
x = 0/2
x = 0

x + y = 5
0 + y = 5
y = 5

x = 0
y = 5

Answer 2

x + y = 5
x -  y = -5
---------------
2x     =   0

x= 0/2

x + y = 5

0 + y = 5
y = 5