Modulo Arithmetic Article Added

A good morning's work! I have now finished the Modulo Arithmetic article — one of my favourite topics. I had to resist the temptation to keep adding more interesting, but definitely irrelevant, results in modulo arithmetic. 😂

Anyway, I hope you all find it interesting! I am also currently working through the next article on sequences and summations, which I have been writing on and off for the past few days, as there is quite a bit of relevant material to cover.

With some luck, I might finish that one today too.