It has grown 23-5=<<23-5=18>>18 feet

So it is 18/3=<<18/3=6>>6 years older

That means it is 6+1=<<6+1=7>>7 years old

# Answer

7
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Tom plants a tree that is 1 year old and 5 feet tall.  It gains 3 feet per year.  How old is it when it is 23 feet tall?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
7
Tom plants a tree that is 1 year old and 5 feet tall.  It gains 3 feet per year.  How old is it when it is 23 feet tall?
train