1.	a. well-defined. b. well-defined. c. not well-defined. d. well-defined.
2.	roster form{10, 11, 12, 13, … }; set builder form {x: x is a natural number x > 10} (Or {x: x is a natural number x > 9})
3.	a. true b. true c. false  d. false e. false  f. true
4. a.		          b.   

5. a. A  (B  C)                                 (A  B)  C     The two sets are not equal.

b. (A  B) is represented in the horizontal stripes, (A  C)  in the vertical ones, so (A  B)  (A  C)  is the checkered area. So (A  B)  (A  C) = A  (B  C) shown above. 
                
6. a. A  (B  ) = {1, 2, 3, 4, 5, 6, 7, 9, 15}  
b.	(A  B)  (C  B) = {1, 2, 4, 5, 7, 8, 10, 14}
c.	 = {9, 11, 13, 15}
d.  = {1, 3, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15}
e.	(A  B)  C = {1, 3, 5, 7, 9, 15}
f.	A  (B  C ) = {1, 2, 3, 4, 5, 6, 7, 9, 15}
7. 40 
8.        

                         (A  B) – C                           (A – C)  B

9.  a. {January, March, May, July, August, October, December}  b) {March, July, August, October, December}  c.    d. {February. April, September, November}  e. U   f. , {January}, {September}, {January, September}  g. 128