Today a father's age is five times his son's age. Exactly three years ago, the sum of their ages was 30. How old is the son today?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Today a father's age is five times his son's age. Exactly three years ago, the sum of their ages was 30. How old is the son today?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
6
Today a father's age is five times his son's age. Exactly three years ago, the sum of their ages was 30. How old is the son today?
train