Respuesta :

a + b = 8
a - b = -4

a = b - 4
(b - 4) + b = 8
2b - 4 = 8
2b = 12
b = 6
a + 6 = 8
a = 2

a = 2
b = 6

2 + 6 = 8
2 - 6 = -4
Use these formulas:

x + y = 8
x - y = -4