Assuming you're asking about a phone number, then you answer thus: mi numero de telefono es XXX-XXXX. However, literally my answer would probably be: my telephone is the black one.
Cual es tu telefono = What is your telephone number
Cual es tu numero de telefono in English literally translates to "What is your number of phone?" Which really means "What's your phone number?"
cual es tu numero de telefono = what is your phone number cual es el numero de telefono = what is the phone number
What is your cell pnone number
It means: What is your phone number?
Well, honey, "cual es tu numero de telefono" translates to "what is your phone number" in English. So, if someone asks you that, you can simply respond with your phone number. Just make sure it's someone you actually want calling you!
cual es tu apellido means what is your surname so you would with respond with your last name.
cual es tu means 'what is your....' (informal)cual es su means 'what is your....' (formal)
Cual es tu nacionalidad means "what is your nationality". So you would reply with your nationality ("Mi nacionalidad es....)
Which is your sport.
cual es tu preferida, literally, means (as close as possible: which girl do you prefer? Cual prefieres (sp) is closer to: which do you prefer.
Cual es el poblacion de tu pais means What is the population of your country