x and y have the values of 16 and -16, absolute value makes it so that the distance from a number to zero is what we must account for, and since both 16 and negative 16 have 16 points of difference to zero, these are plausible answers.
They will combine to equal zero if and only if one is positive 16 and the other is negative, thus showing that if the relationship has a given of having to equal 0, then a double positive or a double negative cannot also occur.