sino vs pero

Question

Esta correcto? En la siguiente oracion, pero en vez de sino esta usado. Creo que despues de negativo sino debe haber usado no?

Vuestros papeles no eran fáciles de entender, pero los nuestros sí

Your papers were not easy to understand, but ours were.

Answer

Hola Robert,
We can use "pero" in this sentence because pero can also be used in negative sentences. When this happens, the sentence with pero is contrasting with what was said before but also "adding" information. You will see it better here in our specific lesson on "Difference between pero, sino, and sino que". This is explained at the bottom of the lesson on a special note that says "pay special attention to negative sentences". Have a look.
I hope it helps.
Un saludo
Inma