"Which way does the path go?"
Aw carrot, a 6 month old question that still doesn't know one of the Kanji...
どっち is just a more colloquial form of どちら. You should be able to use either in the same way as far as Duolingo is concerned.
It is a colloquial form, but it is also used when the options are limited to 2. どちら is used for 3 plus options.
I'm afraid that my answer was a bit over-simplistic. どちら can be used for more than 2 options when referring to places. In a way, however, this is almost a separate definition or usage of the word.
It is explained in more detail in the link below, although どっち is used in DL as a suitable replacement for どちら in describing more than two paths: https://japanese.stackexchange.com/questions/14997/can-%E3%81%A9%E3%81%A3%E3%81%A1-mean-which-one-of-many
It sounds much more natural in the standard form, with the topic first: 「みちはどっちにいきますか？」