24. A={2 la puterea k, unde k ia valori de la 0 la 4}
25. elementele comune sunt {22, 33, 44, 55, 66}
27. a) A={27, 81}
b) B={4, 5, 6, 7, ...., 25}
c) C= {100, 599}
d) D={1, 8, 15, 22, 29, 36, 43, 50}
e) E={7, 8}
f) F={50, 52, 54, 56, 58}
g) G={0, 3}
h) H={0, 3, 9, 27, 81}
28. a) B={2, 9, 16, 23}
b) A={21, 22, 23}
B={52, 55, 58}
30. B={0, 5, 65, 645 }
31. A={9, 19, 29, 39, 49, 59. 69}