What plus what equals -30?

Answer 1

There are many possibilities.

-30 + 0 = -30

-31 + 1 =-30

-32 + 2 = -30

1 + (-31) =-30

2 + (-32) = -30

20 + (-50) = -30

30 + (-60) = -31

Answer 2

There are infinitely many possible answers. One such is (-2.5, 32.5).

Answer 3

-10 + -20