I thought I'd show you an example of は…が… that may be confusing. It has to do with asking "what kind of…?" Let's say we want to ask in Japanese, "What kind of coffee do you like?" Although there is a phrase for "what kind of" in Japanese, it is not used in the Japanese equivalent of this English question. Instead, we ask,
コーヒーは何が好きですか?
Ko-hi- wa nani ga suki desu ka?
To an English speaker, this sounds like an odd way to ask, "what kind of coffee", but は is used to designate the topic of the question, and allow us to ask "what kind of coffee do you like?" in Japanese in this way.
The sentences like 私は頭が痛いです。 or 私はお腹が空いています。 are called は・が文 "wa ga sentence" in Japanese grammar. は indicates the subject, and the rest is an explanation about the subject in this sentence construction. Also, the two nouns preceding は and が have a specific relation. The noun preceding が is a body part, property, a family member, etc of the one preceding は.
e.g.
象は鼻が長いです。
Elephants have a long nose.
彼はお父さんが先生です。
His father is a teacher.
"Noun A は Noun B が~" is often rephrased as "Noun A の Noun B は~" in this case.
e.g.
象の鼻は長いです。
彼のお父さんは先生です。
Also, 私はコーヒーが好きです。 is another type of は・が文. The predicate is an adjective or stative verb (e.g. ある, いる, できる, 要る), and が indicates the object in this case.
e.g.
彼は音楽が好きです。
He likes music.
彼女は料理ができます。
She can cook well.
However, コーヒーは何が好きですか? doesn't belong to は・が文. in this question, コーヒーは is the topicalization of コーヒーで. で is disappeared behind は. In fact, it can be rephrased as コーヒーでは何が好きですか?, and で appears in an answer コーヒーで好きなのはモカです. (Incidentally, が and を are always disappeared behind は when it's topicalized, but other particles can be used with は, e.g., には, へは, からは, よりは, とは.)
This で indicates "range/area".
e.g.
彼はクラスで一番背が高いです。
He is tallest in our class.
映画で一番好きなのはロードオブザリングです。
The movie I like best is The Lord of the Rings.
What is the difference in meaning?
Let me add some supplements.
は works as a contrastive marker there, so 私の本は返してください。 implies that "you don't need to return other people's book(s), but please return my book" or "you don't need to return other things than my book, but please return my book". "My book" and "other people's book(s)" or "other things" are in contrast.
は introduces a noun, the topic. に also introduces a noun but does not introduce the topic.
I think the word "introduce" made confusion. As you might already know, に, が, を, へ, から, と, etc. are called "case particle" (格助詞) in Japanese grammar. Case particles are mostly attached to nouns, but は can be attached to other particles, adverbs or conjugation forms of verbs or adjectives other than nouns. To indicate the topic is not the only one function of は, as same as に has many functions.
e.g.
彼とは話さなかった
いつもは行かない
食べはしない
高くはない
8. Please speak slowly.
ゆっくり話してください。
Correct.
9. Please come with me.
私といてください。いて
This had me stumped so I listened to the audio of the answer. As i predicted と and 行く. However google keyboard godan input did not offer 行て as i would have expected.
That's because the -te form of 行く is not 行て. Try again. (Incidentally, "to come" also can be translated as 来る depending on the context.)
10. Please call me tomorrow. 私に明日電話をかけてください。
Correct. The word order 明日私に電話をかけてください。 sounds more natural, though.
11Please bring your freind.
あなたの友だちを連れてくてください。
Check again what the -te form of 来る is.