I agree fully with JohnApel. Both I and others have mentioned this in relation to other lessons. In English you can't "come" to some place that is away from the speaker; you have to "go" there. The German verbs "kommen" and "gehen" do not mean exactly what the English "come" and "go" mean, and word-for-word translations using them don't always work.
I think you just have to accept that it's another bad translation to make sure you know what "kommen" means. I do think they should accept "go" because that is how it would be said in English and Duo isn't a stickler about literal translation in other places.
"zu" always takes the dative case. "zum" is a contraction of "zu" and "dem", and "zur" is a contraction of "zu" and "der".
zu dem Haus ("dem Haus" is the dative of "das Haus") -> zum Haus
zu der Schule ("der Schule" is the dative of "die Schule") -> zur Schule
Chris, it's the same concept as einem vs einer and dem vs der den etc. They conjugate their base propositions to respective case or tense and we don't. We'll just have to get used to it. I'm making a chart. But once you learn the basic Dativ (indirect object) case or accusativ (direct object) case forms, those endings pretty much work for all the propositions. I believe the original ones we learned were nomativ case so the new cases confuse us. I compare the confusion with Spanish present and past. The endings they use are now in reverse but i got used to that and I'm gonna get used to the German way too. Don't forget to conjugate aus (from) with the correct Dativ case article. And gegen (against) with the correct Akkusativ Case article. Good luck!
Good list of propositions Raymond. Saving it. Thanks. To answer your question i guess you just have to remember those are Dativ and others are Akkusativ, still we haven't learned yet the other cases i saw there was one that starts with a g. I forgot what it's for. See my post above. Maybe that will help you from an American English speaker perspective.
Those in farther English speaking countries have no idea what the Rhine is so we write Rhein because it's a proper noun and we don't know what else to do with it. Good to know but it's gonna take a lot longer to learn German if i have to learn every facet of world geography too!