a) so the quantities that are changing should be the time, and the number of bacteria.
b) This is really similar to compound interest or half-life questions.. I'm thinking something like
where B(t) would be the number of bacteria at minute t. and is the starting number of bacteria (in our case, 1). So we can see that in 5 minutes, we'll have 2 bacteria, 10 minutes we'll have 4, etc.
The rest of the questions involve using this formula (if it's right... I think it is).
Hope that helps! (Hope you learned from it too!)