p.7: 9,18,29,35
p.14: 7,14
p.16: 9,14,15
p.18: 3

p.28: 4,8,12,13
p.37: 2,6,8,10,14
p.41: 6,8
p.44: 4,6,8,10

p.48: 2,10
p.51: 10
p.53: 6,8,10
p.57: 2,4,6,10

p.60-61: 2,6,8,10
p.100: 6,8,12,14,18,20.

p.110: 6,7,12,20,25,29
p.118: 4,10,17,20,24

Prove that in any group of 100 people there are at least 15 people born on the same day of the week.

Show that among any 5 integers one can find 3 numbers so that their sum is divisible by 3.

Given 12 different 2-digit numbers, show that one can choose two of them so that their difference is a two-digit number with identical first and second digit. Show on an example that this conclusion does not hold if we choose 11 numbers.

Prove by contradiction: If infinitely many objects are put into finitely many boxes, then at least one of the boxes will have infinitely many objects.

p.72: 7,8
p.77: 4,5,8,10,14

p. 169-170: 2,8,10,12,16,18,25
Day's book: Problem 2.24.

p.145: 4,8,12,18,26
p.153: 8,14,18,21,24,26

p.178: 10
pp.182-183: 2,6,13
p.187: 2,6,8
p.204: 6,10,14

p.222: 2,8
Let |A|=|B| and |C|=|D|. Prove that |A \times C|=|B \times D|.
p.228: 4,15
By using Cantor-Bernstein-Schroder Theorem, prove that intervals [0,1] and (0,1) have the same cardinality.