how to determine which number a text came from when the contact has multiple numbers I received a text from a contact that has multiple numbers.  I'd like to reply, but I don't know which number to reply to.  

I can't simply reply normally because the text was sent to several people and I'd like to only reply to the sender.

I'm on a Samsung S4.

My specific question: how can I see which actual number a text was sent from, not just the contact it came from?
When you reply in the same conversation, that reply should go to the same number. Is it not?  Check that number shown on the very top of the conversation. It is the number you are currently replying. If you click that number the contact (or popup) will open showing all the numbers attached to that particular contact.

You should be able to choose a different number to message with this option.