Answer:
12
Step-by-step explanation:
The cardinal number of a set is the number of element in the set. Given the set A = {{3, 5, 7, ... 25}}, you can see that the elements of the set are odd numbers from 3 to 25. Writing out the full set;
A = {{3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25}}
Counting the total number of element in the set, you will see that there are only 12 elements in the set. Hence the cardinal number of the set is 12 i.e n(A) = 12
