42 = 101010_2 in base 2. (verify this if you are not comfortable with bases, since from this point on I will assume you can do this yourself) Using this fact and the squaring trick, compute 342 (mod 13). Now, do this problem with Fermat's Little Theorem. You should get the same answers. (This always applies, but just stressing) Your proofs should be "by hand". This means every step should be followable by a human. Feel free to check with a computer, but your writeup (as they will be on exams) must be done as if a computer were not there.