Translation:This woman employs both architects.
The last one was "oboje". It depends on the gender, it depends on the case, I wouldn't say "number" since this means "both", so it's always plural ;) Well, let's try. We have:
oba - for masculine and neuter nouns, but not personal. Oba pudełka, oba drzewa, oba psy, oba koty.
obie - for feminine nouns. Obie kobiety, obie szafy, obie książki, obie policjantki.
obaj - for masculine personal nouns. Obaj chłopcy, obaj mężczyźni, obaj policjanci.
oboje - when you mean:
two specific living beings (two people or one human being and one animal) of different genders
two specific living beings, when one of them is grammatically neuter. For people there are not many more than "dziecko", several animals can be grammatically neuter, so let's say "słoń i emu" will be "oboje".
also for "dzieci", regardless of the children's gender
also some nouns that normally take a collective noun, like "oczy" and "uszy": oboje oczu, oboje uszu.
"oboje" takes Genitive, unlike the others which just take Nominative.
"zatrudniać" takes Accusative.
I feel like my brain is dying on this... That one is pretty impossible to learn for me xD But thanks for making the endings clear here :). So there's 16 different ways to say "both" depending on the case and gender or so + 4 - do the synonyms have declension patterns or they're just used in nominative case? I mean the obydwa", "obydwie", "obydwaj" and "obydwoje.