What will always be the result of a negative plus a negative?

-6+-7=-6-7=-13

if this is what you mean, the answer will always be negative  

BUT

-6 - - 7 = -6+7= +1

-6- - 2 = -6+2 = -4

5 - - 12 = 5+12 = +17

Actually, if you add a negative number to its value in positive numbers, the answer is zero.

EXAMPLE:       -654 + 654 = 0

the answer will always be positive unless you do negative one plus negative one.