It could also refer to a border collie, kelpie, or many other breeds - or it could be a mutt, who knows - and dalmatians aren't really that common (at least where I live) because they're incredibly high-maintenance pets, but were popularised by the media (cough 101 Dalmatians cough), thus leading to an influx of neglected/abandoned dogs from owners who couldn't handle them and breeders going overboard. Then again, they do that anyway in most parts. Oops, this kinda turned into a rant. Sorry.
To me the sentence only implies 1 dog, that is colored black and white. If there were 2 dogs, as your translation suggests, I believe it would be "Nous avons un chien noir et un (chien) blanc." But a native speaker might have better explanation/translation. My French can be sloppy at times.
'We have a black and a white dog' implies that there are 2 dogs!!! That sentence implies there is a black dog and another dog that is white, but the correct translation 'we have a black and white dog' implies that the dog has 2 colours which IS possible... I think you are missing te point a bit
You added the English word that to your translation of the French. The computer does not see that in the French so it marks your English translation wrong.
Sometimes Duo will let you add a word to the English translation if it is necessary for the English to make sense. However, in this case, we have a black and white dog makes perfect sense in English. No added words are necessary.
"Nous avons un chien noir et blanc." Literally translates to "We have a black and white dog." The "and (et)" is not indicating a separate dog, but rather a separate color from the first. If it wanted to talk about 2 different dogs, it would say either "Nous avons un chien noir et un chien blanc." OR "Nous avons duex chiens, un blanc et un white." I am pretty sure.
Languages, although they influence each other over time, have their own grammar. Words do not have to be "reordered". They are in a certain order in a certain language, and often in a different order in a different language, which is not the same as saying that they have to be reordered.
Un chien means only that the gender of the dog is unknown. If you use either male or female in the English translation you are including information that is not in the French sentence.
In the French sentence, you have to use either male or female gender. Male gender is used to refer to any animal/s not known to be female. When you use chien you are saying only that you do not know if the dog is female, not that you know the dog is male.
I get it now. Many and I do mean many years ago -the 70's - almost my entire first year university French was surprised to learn the words chatte and chienne even existed, we thought that all animals were designated to be male, and for many of us it was our first introduction to the pronoun tu. Thanks I guess I have more catching up to do than I thought.
The french sentence is: "Nous avons un chien noir et blanc." If we simply convert the french words to english words we get, "we have a dog black and white." In a sentence usually certain words go together so in the given case we can break the sentence up into parts to see what we have - [we have a] [dog] [black and white] - In this case simply rearranging the words we get an english translation, [We have a] [black and white] [dog]. Translation is not always going to be this simple but it is a good place to start if you are having trouble.
The important part of translating the sentence is to recognize that there is only one dog which happens to be described as having two colours, black and white." If the sentence was referring to two separate dogs the french word would have been 'chiens' for plural (dogs) not 'chien' for single (dog). Also 'un' is used for singular objects and is like say one of something, in this case, a dog (one dog).
Also, 'and' is a linking word and there is no natural way to split the words black and white in the sentence. In reference to your translation, "We have a black dog and white," it is unnatural to split the two colours (or other linked words) joined by only an 'and,' it would require an extra word such as 'a' in order to separate the words which would result in a different meaning i.e., "a black dog and [a] white," changes the original meaning from, "one dog (that is both black and white in colour)," to, "one black dog and one white [dog?])." A correct translation requires that any added or changed words do not change the original.