Is this a proper composition? Which do you prefer 20 or twenty? Or are they both correct?
ex)I'm twenty(20) years old. Don't talk to me as if I were a child.
I spell out a number if it is under 10 and use the numerical form if it is more than nine. "I first met her when she was only two and didn't see her again until she was over 30". There is a rule stating that you should not begin a sentence by using the numerical form - Twenty years ago, not 20 years ago.