I can help with the last one since i don't know the specifics of the loan thing. For the last one, though, N is the end amount of bacteria;

is the initial amount of bacteria; e is Euler's number, which is a constant; and t is time in hours. So our equation would look like this:

. First divide both sides by 100 to get

. The only way you can get that k down out of the exponent is to take the natural log of both sides:

. Of course taking the natural log of the right side undoes the e, and the natural log of 14.32 can be found on your calculator, so we have now 2.6616 = 5k. Divide both sides by 5 to get that k = .53