about suchО таком is used with a masculine or neuter singular noun; the form changes to agree with the noun, as in о такой or о таких.
RU: Мы говорили о таком важном решении.
EN: We talked about such an important decision.
phraseUncommon#20,636
about thatLiterally “about such”; used to refer to something mentioned or understood from context. The form такой changes to match the noun it refers to.