Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: dan ' s age after 20 years will be 7 times his age 4 years ago . what is the present age of dan ?
8
Dan's present age is 20 less than 7 times his age 4 years ago.