How old are Dan and Julie?

Dan is 54, Julie is 36.

First we have total age of 90 years.
We also have number 3 (three times), number one and number one again.

So, we have 5, and by deviding 90 by 5 we get 18 - the Julie's age when Dan was as old as she is now.
Then we do 18 three times and get 54 - current Dan's age. Then 90 - 54 = 36 - current Julie's age.