Jawaban:

18.P = {x|x < 8, x ∈∈ bilangan asli}

P = { 1,2,3,4,5,6,7}

n(P) = 7

A. 7.

19) yang merupakan himpunan kosong

A. {bilangan prima antara 7 dan 11}

20) A = {4, 6, 8},

B = {1, 2, 3, 4, 6},

C = {0, 2, 4, 6, 8, 10}

B. A⊂C

21.A = {x | 1 < x < 20, x bilangan prima}

A={2,3,5,7,11,13,17,19}

B = { y | 1 ≤ y ≤ 10, y bilangan ganjil}

B= { 1,3,5,7,9}

A ∩ B = A. {3, 5, 7}

22. K = { x | 5 ≤ x ≤ 9, x bilangan asli }

K ={5,6,7,8,9}

L = { x | 7 ≤ x < 13, x bilangan cacah},

L={7,8,9,10,11,12}

K ∪ L ={5,6,7,8,9,10,11,12}

B. {5, 6, 7, 8, 9, 10, 11, 12}

23.P = {2, 3, 5, 7, 10, 12}

Q = {1, 3, 5, 7, 9}

P − Q ={2,10,12}

C. {2, 10, 12}

24.(20 -8) + 8 +(15-8)

= 12+8 + 7

=27

B. 27 siswa

25.40 =(2p-5) + 5 + (p -5) + 9

40 = 3p-5+ 9

40-4 = 3p

36 = 3p

p = 36/3

p = 12

C. 12 orang