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How to compute $213^{-1}$ modulo $466$?

Could you also provide me with an explanation of how to do it?

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    What is the idea behind posting a question, and then replacing it with one that's entirely different? How long will the current question stay up, before you decide to change it, too? Anyway, the answer to your question is in every introductory number theory textbook ever written. Do you have access to a library?2012-05-20
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    Not to mention the net, e.g. [wikipedia](http://en.wikipedia.org/wiki/Extended_Euclidean_algorithm)!2012-05-20
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    Well, it's a long story with the question content, I am trying to help someone and it seems that she is constantly changing her mind :) Could you point me out to some mathematical resources?2012-05-20
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    Relevant resources will be found at QA 241 (Library of Congress system) or 512.81 (Dewey decimal system). Or type "modular arithmetic" into Google.2012-05-21

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So you want to compute the inverse of $213$ modulo $466$? In other words you want to find $x$ such that $$213x\equiv 1\text{ mod }466.$$ More specifically you want to find $x$ and $y$ such that $$213x+466y=1.$$ Have you heard of the Euclidean algorithm?