The word "su" in Spanish possesive determiners
The word "su" has a lot of meaning such as: his, her, your (formal), their. How can I discriminate them? Please help me with this! Gracias!
The only real way to tell them apart is by context. Basically, you have to have had some information previously to know what 'su' means in any given sentence. That's why Duolingo usually accepts every meaning of su in its answers, because it's not very good at putting the questions it asks in any real context.
¿Por qué están los niños en su casa? Porque su madre fue de compras = Why are the kids at your house? Because their mother went shopping
But this could easily be: 'Why are the kids at her house? Because your mother went shopping' and several other things too. You wouldn't really know for sure unless you're actually involved in that conversation
Context. Think of this: "The word "mine" has a lot of meanigs such as: mía, mío, mías, míos. How can I discriminate them?"
In "Vi a Pedro y a Juan saliendo de su casa" is impossible to determine the owner. Pedro? Pedro and Juan? Juan? Another person??? You need the rest of the story.