Question 429189
If the money is invested at 11% compounded weekly, then its' effective yield is (.11/52)^52, or 11.615% yearly.  Compouding yearly, we get 11.615% yearly to the 16th power, or 480.78%.  To find the starting principal we need to divide $80,000 by the principal plus 480.78% of  the principal.  Thus we get:

principal: $80,000/5.8078 = $13,774.58