Make какћй/такћй agree with long adjectives and nouns.
Use uninflected кђк/тђк with other things (short adj., adverbs, verbs).
Какћй гћлос! What a voice!
Какћй у неё приїтный гћлос! What a pleasant voice she has!
Ћн такћй џмный! He's so intelligent!
Онђ тђк хорошћ говорќт по-рџсски! She speaks Russian so well!
Не нђдо тђк говорќть. You mustn't talk like that.
Онђ тђк занятђ! She's so busy!