"Do you see his books?"
Translation:Ты видишь его книги?
First thing to consider here is the fact that this exercise asks for books, i.e. plural form of book. This means that you are going to apply plural rules for inflecting this noun in the accusative case.
Second thing to consider is that book is inanimate, "not alive". This means that we are going to use the nominative plural case (книги) for forming the accusative plural. (If the noun would be animate, you would use genitive plural.)
You can find all the inflections below for this noun.
Ты and Вы both mean "you" but address the same person with a different level of formality. They can be used in the same situations depending on how mutually familiar your are with the other person. Вы can also mean a group of others as well, but I think Duolingo is trying to show how in the singular sense only how Ты + conj. and Вы + conj. can be used in the sentence without changing the intended audience or just get you used to the fact that they mean the same thing grammatically.
Can someone help me with the word order please? I answered...
- Вы его книги видите? and
- Ты его книги видишь? I got those two above wrong.
Is it incorrect because the sentence is in the question form? Another question was asking me to translate "I live here" and I answered "Я здесь живу." I got it correct so I am not sure what's wrong with my answer to this quetion.
I don't think your answer is wrong because Russian sentence order is pretty flexible but it's not the standard way of ordering things.
As far as I can tell, Russian ordering is usually the same as English, except for a couple of things: 1. They prefer to not have adverbs like здесь and уже at the end of the sentence. 2. They also do not like having short personal pronouns like вас, его etc at the end of the sentence so they will usually be moved to before the verb.