"The woman has one apple, the man has two apples."
Translation:Femeia are un măr, bărbatul are două mere.
”Unu” is not accepted because in the English sentence you have ”one apple”. Unu is the number when you count one, two, three / unu, doi, trei. If you want to say ”one + noun”, like here, one apple, you will have to use ”un măr”, like the indefinite article. If you put it the other way around, the man has two apples, the woman has one, you can say bărbatul are două mere, femeia are unul. With an L at the end of unu, unul beeing a pronoun in this case. https://dexonline.ro/definitie/unul
It's neuter. So it's treated as masculine in the singular and feminine in the plural.
What´s the difference between doi and două ? I am just a fresh student of Romanian and you can imagine how difficult is turning out to be this language for me. It is really a hard nut to crack!