Translation:Please read page 7.
I don't think the Duo course goes into the intricacies of Japanese numbering (where there are specific counters for round objects, long-and-thin objects, flat-paper-like objects, etc.), but i recommend Tae Kim's free Japanese grammar guide (Google it) to fill in the gaps this course misses.
I think both readings are possible, but you need to figure out the right one by the context. My guess is that "Nページを" references "page N", whereas "Nページ" means "N pages". Here are a few examples I found on WWWJDIC:
Making references to number of pages:
私は更に５０ページ読んだ。 = I read fifty pages further.
私は６０ページ読んだが、一方彼は１０ページしか読んでいない。 = I have read sixty pages, while he has read only ten.
Making references to a specific page:
９４ページを読んで下さい。 = Please read page ninety-four.
日本地図の３ページを開けなさい。 = Open your atlas of Japan to page 3