We most often talk about people’s ages with be + number
He is thirty. (NOT
He has thirty.)
Also, be + number + years old (more formal: … of age).
He is thirty years old / of age. (NOT …
We ask How old are you?, not normally What is your age?
Note the structure be + … age (without a preposition).
- When I was your age I was working. (NOT
When I was at your age… )
- The two boys are the same age.
- She’s the same age as me.
In other structures, at is common before age.
He could read at the age of three. (NOT …
in the age … )
At your age, I already had a job.