Study questions...need to know how for exam

I have a set of problems that I don't know how to do. I'm using them to study for my exam, so please show a step-by-step or at least a basic idea how to do it.

1)

2) Evaluate:

3) Californium-252 has a half-life of 2.645 years. If the equation describing the decay of the readioactive nuclei is given by , find:

a) the value of k

b) how long it will take for 95% of the radioactive nuclei to disintegrate.

4) Solve:

I don't even know what I'm supposed to do on this one...(Wondering)

5)

6) Use with k=.001 and M=150 to write y as a function of t.

Thank you!!!