Why puede instead of puedes?

How come when you ask someone to take your photo, you say " puede sacar mi foto?" instead of "puedes sacar mi foto?" I thought puede meant can he or she.

I can explain this best by including a pronoun in the sentence, that is say "puede usted sacar mi foto". The sentence uses the formal singular conjugation. Similarly, the second sentence can be rephrased as "puedes tu sacar mi foto". Since it is generally clear who we are talking to/about, the pronoun is usually omitted.

Oh, thank you. That makes sense.

This was frustrating for me when I first began learning. Sometimes the lesson would use the second person singular, then in another place in the lesson the to third person would be used. It took me a long time to realize what was going on: sometimes you can use the second person informal, other times the formal should be used. For a long time I just thought I was wrong and would score myself less than perfect on the tests. Now that I understand the reasoning I am able to see when the other form can be used.

So when you are asking someone to take your picture it is most likely a stranger and in that case the formal should be used?

Yes. Absolutely.