Math 7 grade 7. can anyone me answer these questions?

1. what is the opposite of -2?

2. when we add opposites together they will always equal = ?
-1 1 or 0

this is also known as what ?
additive inverse or opposite addition or inverse?

adding with integers with same signs.

-8 + -3 = ?

-12 + -15 = ?

-3 + -9 + -25 = ?