Applications of Exponential and Logarithmic Functions

Hey guys, this is my first post and I would like to be active on these forums and help others where I can.

I ran into some problems that I couldn't find a solution to. There are three questions I'm struggling with and there all somewhat related in a sense.

1.The amount of particulate matter left in solution during a filtering process is given by the equation https://davenport.blackboard.com/cou...53/f1q23g1.jpg where n is the number of filtering steps. Find the amounts left for https://davenport.blackboard.com/cou...53/f1q23g2.jpg and https://davenport.blackboard.com/cou...53/f1q23g3.jpg. (Round to the nearest whole number.)

-This one makes no sense to me and I tried plugging in the n values. maybe I am suppose to be taking the log of the equation??

2. How long will it take a sample of radioactive substance to decay to half of its original amount, if it decays according to the function A(t) = 200e-0.131t, where t is the time in years? Round to the nearest hundredth year.

-This question I feel like I don't know what to plug in or how to go through finding the correct solution.

3. Use the formula N = Iekt, where N is the number of items in terms of the initial population I, at time t, and k is the growth constant equal to the percent of growth per unit of time. A certain radioactive isotope has a half-life of approximately 1750 years. How many years would be required for a given amount of this isotope to decay to 20% of that amount?

- I tried setting this up in this way. ln(.5) = 1750 this came out to .000120547(can I stop after the 0 and leave it as .00012? Not sure If I'm doing this one right either and these three questions didn't seem like rest of them and I can't figure out!