what is the age of you?对吗？

可以，但不地道.

可以说

What bout your age? 或

How old are you ?

不可以。正确表达应为：
What's your age please?
May I know your age (please)?
How old are you?

望满意。

what is your age较地道

- -~!

当然可以啦～～

你想问年龄多大是吗？那应该说 how old are you?

应该说：How old are you?