Assume that when adults with smartphones are randomly selected, 36% use them in meetings or classes. if 6 adult smartphone users are randomly selected, find the probability that exactly 4 of them use their smartphones in meetings or classes.

There is 36% chance that an adult use smartphones in meetings or classes, which also means 64% that they didn't.

If you select 6 adults and find that exactly 4 of them use the smartphone, 2 of them would be not using it. The probability of this question should be independent and the order is not important. The calculation would be:

The chance is independent so, the calculation would be:
using smartphone^4 * not using smartphone^2
0.36^4 * 0.64^2= 0.006879

The order is not important, so you need to calculate the number of ways
The number of the ways to take 4 things out of 6:
6C4= 6*5/2= 15

Multiply both numbers you will get: 0.006879*15= 0.10319= 10.319%