Tujis cullal.. format tools add-ons normal text - arial all changes saved in drive 12 bi ua e 1 12 13 14 15 16 problem 3.3. prove that if a is a subset of x, then a) a n (x - a) = ø. b) au (x - a) = x c) x-(x-a)=a. hint: use a)and b). problem 3.4. prove that if a and b are subsets of x, then a) a-b = an (x-b). b) x- (anb) = (x - a) u (x-b). c) a s b if and only if x-b sx-a. • problem 3.9. let a and b be sets. prove that axø = øxb = 0. problem 3.13. is the following true? prove it or find a counterexample. for any sets a, b,we have 2an2b s2anb.