I cant quit figure this question out

Question

The amount (in pounds) of a particular radioactive material stored in a concrete vault is modeled by the function

                 A = A₀e^-0.0069x ,

where x is the number of years since the material was put into the vault.

If 500 pounds of the material are initially put into the vault, how much time will need to pass until only 330 pounds remains? 

Answer 1

In the formula; A₀ represents the initial amount,

A represents the remainder amount

330 = 500*e^-0.0069x 

330/500 = e^-0.0069x 

ln(33/50) = ln(e^-0.0069x )

solve this equation and you will find the answer