Again there are differences between formal written and colloquial spoken Tamil.
"How old are you?" has been translated in these three ways:
ungalukku ethanai vayasu?
ungalukku evvalavu vayasu achu?
unga vayasu enna?(this is the most casual spoken language)
The answer, "I am ____", or "I am _____ years old." is:
enakku ______ vayasu.