What is negative plus negative?

Answer 1

Same thing as negative minus positive. You may as well imagine both are positive, add them, and then add a big fat "-" in front.

Consider this, -X = -1 • X, and vise-versa. So if -X is -5 -3, then that's the same as -1(5+3), which is the same as 8 • -1.

Negative.