Here's why:
* "Cual" is used to ask "which" or "what" but it's not used for asking for someone's phone number.
* "As" is not a word in Spanish. It's likely a mistranslation of "es" which means "is".
* "Tu numero de telefono" is correct and means "your phone number".
Here are two correct ways to ask for someone's phone number in Spanish:
1. "¿Cuál es tu número de teléfono?" (This is the most common and formal way to ask.)
2. "¿Me puedes dar tu número de teléfono?" (This means "Can you give me your phone number?")
So, the correct translation of "Cual as tu numero de telefono" would be: "What is your phone number?"