Given that the absolute value of a is 8, the absolute value of B is 4, and the absolute value of a + B = - A-B, try to find the sum of all the values of a + B

Given that the absolute value of a is 8, the absolute value of B is 4, and the absolute value of a + B = - A-B, try to find the sum of all the values of a + B

If a = - 8, B = - 4, then a + B = - 12
If a = - 8, B = 4, then a + B = - 4