I get tripped up by this all the time. In Australia, we use "going" instead of "doing" (which is the north american preferred phrase). Given that "going" is the direct translation of the French, it should certainly be accepted by DuoLingo. I also translate all the similar phrases similarly, such as "Comment va-t-il?" to "How is he going?".
Thanks. Didn't realise it was colloquial Australian English. http://www.immi.gov.au/living-in-australia/choose-australia/about-australia/au-customs/common-words.htm