To find this, we will find the number of combinations of 5 country songs taken 5 at a time, 6 pop songs taken 0 at a time, and the total number of outcomes will be 11 songs taken 5 at a time:
In a geometric sequence you are just multiplying basically. To go from 36 to 24, you multiply by 2/3, and the same will be with the next term. When you multiply 24 by 2/3 you get 16.