How to explain inverse modulo? [closed]

Do you know a (simple) inverse modulo calculator somewhere on the Internet?

How to explain simply inverse modulo? (when the concept of modulo is already a bit known)

How to explain someone how to find a calculation resulting with a given modulo? For instance, finding a calculation with a modulo = 5.

• I'm not sure this is a good question for this site since it asks a question about how to calculate something instead of a question about mathematics education; you can find inverses modulo $n$ with the Euclidean Algorithm. See for example the "Extended Euclidean Algorithm" section at en.wikipedia.org/wiki/Modular_multiplicative_inverse May 16 '17 at 16:50
• And how to explain also... But do you think I should move my question? May 17 '17 at 10:03

a = Mod(3,7)

This gives 4 and 5, respectively.