From the list of the first 10 positive integers, A={1,3,5,7,9} and B is the set of primes less than 10. Therefore Pr(A’) and Pr(A only ) are,
A' refers to the complement of A, which includes all the elements that are not in set A. In this case, the first 10 positive integers are {1,2,3,4,5,6,7,8,9,10}. Since A={1,3,5,7,9}, A' would be {2,4,6,8,10}. Therefore, Pr(A') is the probability of selecting an element from the set A' out of the set {1,2,3,4,5,6,7,8,9,10}, which is 5/10 or 1/2.
A only refers to the elements that are in set A but not in any other set. In this case, A={1,3,5,7,9}, and none of these numbers are present in set B, which consists of the primes less than 10. Therefore, Pr(A only) is the probability of selecting an element from set A only out of the set {1,2,3,4,5,6,7,8,9,10}. Since all the elements in set A are only in set A, Pr(A only) is 5/10 or 1/2.