Answer:
The time taken to reach the balance is approximately 13 years.
Explanation:
Given : Mary deposited $350 in a bank account that promises 2.8 percent interest compounded continuously.
To find : How many years will it take to reach a balance of $500?
Solution :
The formula of compounded continuously is

Where, A is the amount A=$500
P is the principal P=$350
r is the interest rate r=2.8%=0.028
t is the time in year.
Substitute the values in the formula,



Taking log both side,




The time taken to reach the balance is approximately 13 years.