Question

A die is rolled 108 times. How many times can you expect to roll a 2?

Answer 1

The die can land in 6 different ways.
Only one of them is a 2.
So the probability of rolling a 2 on any roll is  1/6 .
In a large number of rolls, you expect roughly 1/6 of them to be a 2.

In 108 rolls, you should expect a 2 somewhere around 

                                           (108/6) = 18 times. 

Answer 2

The probability of rolling a specific number on a die is 1/6. Therefore the expected number of times a 2 is rolled in 108 rolls of the die is:
$\frac{108}{6}=18$