Resposta :
x + y= 169
x - y = 31
2x = 200
x = 200/2
x = 100
achando Y
x - y = 31
100 - y = 31
-y = 31 - 100
-y = - 69 x( -1)
y = 69
x - y = 31
2x = 200
x = 200/2
x = 100
achando Y
x - y = 31
100 - y = 31
-y = 31 - 100
-y = - 69 x( -1)
y = 69