for -(-3 + 4) distribute the negative outside the parentheses to both the -3 and the 4

Answer 1

-(-3) = 3
-(4) = -4
so ...

Answer 2

When distributing a negative (-1) outside the parentheses, the signs switch or become opposite.

-1 x -3 = 3 since a negative x negative is always positive
-1 x 4 = -4