"Do you sell school clothes here?"
Translation:Dych chi'n gwerthu dillad ysgol yma?
I don't really think it's fair to be tested on formal and familiar when it wasn't in the lesson. I don't recall seeing it in the tips before the lessons.
It's the singular/plural divide, kind of like tu/vous in French.
- Wyt ti'n is singular/familiar do you
- Dych/dach chi'n is plural/formal do you
What if I wanted to ask one stranger something? Would I use wyt ti'n because it's singular or dych chi'n because it's formal?