I for some reason can't solve this and I have issues visualizing solutions that come with stochastical independence. It seems intuitive for me though, that if $\frac{\mathbb{P}(A \cap B)}{\mathbb{P}(B)} = \frac{\mathbb{P}(A \cap B^c)}{\mathbb{P}(B^c)}$ then $B$ and $B^c$ must influence A in the same way, which implies they do not influence $A$ at all. This is no proof though, I would appreciate some intuitions/ help.
The definition of independence: $\mathbb{P}(A \cap B) = \mathbb{P}(A)\cdot \mathbb{P}(B)$
$$\mathbb{P}(A|B) = \mathbb{P}(A |\Omega \setminus B) \Leftrightarrow$$
$$\frac{\mathbb{P}(A \cap B)}{\mathbb{P}(B)} = \frac{\mathbb{P}(A \cap B^c)}{\mathbb{P}(B^c)}$$
Hint Are you aware of the identity: $$\frac{a}{b}=\frac{d}{c} \,\,\, \text{then} \,\,\,\frac{a}{b}=\frac{d}{c}=\frac{a+d}{b+c}$$ ?