"Baku and Dakar"
According to A. S. Tritton's book Arabic (Teach Yourself Books, p. 40) the conjunction وَ "wa" ("and") is written with the following word, as it is here. Someone was commenting earlier today elsewhere that that is incorrect, that it must be written separately. I pointed the person to the comments that said that it's not always the case--it depends on country. I couldn't find the thread in the searches so I thought I'd bring it up here.
There a tons of Arabic dialects out there in the world. Some of them are so far apart as german and dutch or portugese and spanish. This Duolingo version is an altered MSA - "Modern Standard Arabic" version with the clear intend to speak with most of the arab world, not(!) some dialects.
This won't be the last time you see something different. Just stick with it. Later down the road, you may even start separating MSA and a specific dialect on your own. ;) For example the Egyptian dialect. Which is the most spoken in the arab world due to big influence in the entertainment and media.