Find the cardinal number for the following sets. a = {102, 103, 104, 105 155}       b = {102, 104, 106, 252}

Cardinal number, more commonly called cardinality, is the number of members of a given set.

For example, if P={1,4,6}, cardinality is 3 because there are three member in the set.

For A, the numbers run consecutively from 102 to 155, so there are (155-102)+1=54 members.  The cardinality is therefore 54
Similarly, for B={102,...252}, there are (252-102)+1=151 members.  So the cardinality is 151.

The first answer is correct