"¿Puedo usar estos veintinueve pesos?"
Translation:Can I use these twenty-nine pesos?
Huh? As opposed to some other 29 pesos? And "use?" Use how? Wouldn't you normally ask to have them, or borrow them? Another odd sentence.
It is a weird construction in the abstract, but if you think of it in the context of a conversation, it's not so strange: "We don't have much money left to spend today... Can I use these 29 pesos?" or at a parking meter or valet or something. I've definitely asked my girfriend "can I use this 5?" When a pizza delivery comes and I need a tip.
It is weird, but the point is to teach us vocabulary and sentence structure, not necessarily one sentence that you'll use.
Because the plural of este is estos. Este/esto are the only weird ones---estos is surprisingly normal.
"Can I have twenty nine pesos?" Can I borrow twenty nine pesos or possibly even... Can I use twenty nine pesos? I can't imagine saying or hearing, "Can I use these twenty nine pesos." It's a stretch. Gracias