Verified answer

Example 1. Sono hon wa ano honyasan ni wa nai (That book isn't at that bookstore.) "nai" can be substitute by "arimasen."

Example 2. Sore wa wakaranai. (I don't understand it.) "wakaranai" can be said by "wakarimasen."

Example 3. Hashi wa iranai. ( I don't need the chopsticks.) "iranai" can be said by "irimasen."

masen is more polite way to say "nai." Doesn't exist or no need in iranai's case.

If you want to know the usage of negative form "ない", you can read the following article.

http://www.guidetojapanese.org/learn/grammar/negat...

This site provides clear explanations about Japanese grammar, so you can use it as a grammar reference. And if you want to read more articles, you can visit the following site.

http://www.infocobuild.com/language/japanese/japan...

I don't know if these websites will answer your questions but here are some websites:

http://www.language-global.com/learn/japanese/?p=1...

http://www.derik.org/Gateway/novels/glossary1.htm

http://www.wordiq.com/definition/Japanese_grammar

http://www.all-about-teaching-english-in-japan.com...

HOPE THIS HELPS :)