Translation:I walk fifty meters north.
I missed out the 'I' because it wasnt specified. Is there something in this sentence that implies I am the person walking rather than someone else or an instruction?
Instructions are given in て form always, but other than that, no, there's nothing specifying "I" is the subject.
Instructions have a different sentence form, and the verb might change.
When we see sentences like this, usually we assume the speaker is the one referred to.
E.g: クレアちゃんは、朝学校にどうやって行きましたか? (How do you get to school in the morning?)
五十メーター北に歩きます。(I walk 50 meters north).
It makes sense, because we're answering a question. If we talk about someone else, however, it's either an instruction or an odd statement. It's hard to find a situation where you say something like "you walk 50 meters north" in English without giving an instruction. This would be more like an instruction:
その学校にどうやって行きますか?(How do I get to the school?)
五十メーター北に歩きてください。(You walk 50 meters north.)
we actually went through a whole lesson giving directives with ます-ending sentences, not with the imperative てください requests.
I think that it could be somebody else walking, certainly, but i don't believe it can function as an instruction. somebody please correct me if I'm wrong
No, it's mostly context who the subject of the sentence is. A command though, would use the て form of the verb though.
It probably hasn't been taught yet, but shouldn't へ be used here instead of に?
I agree, I answered it that way as well and I've been speaking Japanese for 30+years. That should be correct.
How come 'km' is accepted instead of fully writing out 'kilometres' but 'm' isn't accepted instead of writing out 'metres'?