18 because it says Cuando yo tengo un año más, Diego va a hablar con mi abuelo para poder salir conmigo. Me gustaría salir con Diego sola, pero por ahora << for now >> salimos con nuestros amigos. Which means When I have one more year, Diego is going to talk to my grandfather so he can go out with me. I'd like to go out with Diego alone, but for now, we're going out with our friends.
17+1=18
-Hope this helps