It's in Cyrillic. The official title is "Четиризначни математически таблици и формули".
https://www.book.store.bg/p35401/chetiriznachni-matematiches...
https://i.redd.it/5ibk260ssqa61.png
e.g. i understood the other two words in the title no problem.
>Ukrainian
i'm from moldova and i speak russian and understand ukrainian pretty easily. calling them distinct languages is true but it's pedantic - it's a very blurry line how mutually intelligible the two languages are.