I won't give the right answers here. If you want to know the right answers, come to see me.
2.1.11 All subsets of a set S, including the null set and S itself constitue the power set of S. This question asks the order of the power set. It's 2^n, where n is the order (size) of S.
2.1.12 Don't forget to divide 2!. Both subsets are of order 3 and are not distinguishable.
2.2.08 Read and understand the proposition on Page 26.
2.2.14 Only one of you got it totally right. A geometric reasoning is more straightforward than an algebraic one. Draw a picture (Hint: a square, a straight line and a hyperbola).
2.3.03 See the similarity to drawing a ball from an urn?
2.4.03 Spend a little more time. Write a Perl/Python/Tcl script to help you. It's a computer science, not a pure mathematics, class. The key space of affine cyphers is very small.