algebra
posted by david .
The amount of money in an account with continuously compounded interest is given by the formula A=Pe^rt , where P is the principal, r is the annual interest rate, and t is the time in years. Calculate to the nearest hundredth of a year how long it takes for an amount of money to double if interest is compounded continuously at 3.8%. Round to the nearest tenth.

so you are solving
2 = 1(e^(.038t))
ln2 = ln(e^(.038t))
ln2 = .038t(lne) but lne = 1
.038t = ln2
t = ln2/.038 = 18.24 yrs 
Suppose you invest $2500 at an annual interest rate of 3% compounded continuously. How much will you have in the account after 7 years? Round the solution to the nearest dollar. ?