The cardinal number n(A) = for A

The cardinal number n(A) = for A = {x : x is an odd prime number less than 20} is
(a) 8
(b) 7
(c) 9
(d) 10

Solution:

If A = {x | x is a positive mutliple of 3 less than 20} and B = {x | x is a prime number less than 20}, then n(A) + n(B) is
(a) 6
(b) 8
(c) 13
(d) 14

Solution:

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