Which number in set A = {9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20} is an element in both the subset of odd numbers and the subset of multiples of 9 ?

The correct answer is: 9

Subset of odd numbers = {9, 11, 13, 15, 17, 19}
Subset of multiples of 9 = {9 , 18}
So, 9 is the number that is an element in both the subset of odd numbers and the subset of multiples of 9.
Subset of odd numbers = {9, 11, 13, 15, 17, 19}
Subset of multiples of 9 = {9 , 18}