I’m an absolute beginner. I was reading a chapter on the dative case in this book called German Basic Grammar by Routledge. I think in the following example of a sentence with two dative nouns, dem Jungen is wrong, at least according to the rule the book gives.
Ich helfe dem Jungen mit seinem Mantel. I help the boy with his coat. (Unit 13, P. 72)
I think it should be either dem Junge (singular) or den Jungen (plural). Am I right?
I know this is a very basic question, but I have less than a month exposure to German language, and it is frustrating when you doubt the book teaching you.