3p=p(1+(.0557/365))^365t. Where, p is the beginning amound at t is the time it takes. You're right, just solve for t. If you need help with that, just ask! :)
EDIT:
Alrighty. So, you divide by p, to get 3=(1+(.0057/365))^365t. Now, we evaluate the inside to get 1.000015616, rounded to 9 decimal places. We now need to use logarithms to figure out what that t is. Trust me on this, or look up the mathematics behind it. We need that 1.0000... as the base for our log, and we need to have the actual subject of the log be the 3. Now that we have log base 1.000015616 of 3, we divide that atrocity by 365. We now get t to be equal to 192.7459133, rounded to 7 decimal places. While this does seem ungodly long, remember that everything in our problem is done in days. So, in reality, that just over half of a year.
