I have just started lesson 5 in Arabic and an arabic character is written in western script as "3a", as if 3 was a letter. I can make no sense of this. What is it about?
The decision was a logical one considering that it was around long before the duolingo arabic course started. In fact, it was already being used before duolingo came into existence. People have been using 3 to represent ع since the early days of the internet. Similary, 7 is used to represent ح
We only have 26 characters, so they had to find something besides letters to represent some of the Arabic ones. Here's a list of some numbers used to represent letters: