The experimental probability, sometimes known as the relative frequency, is the number of times the 'interesting' event occurs divided by the number of events in total that have occurred.
In your case, the 'interesting' event is rolling a 3. This happened 11 times.
The total number of events that have occurred is 7+9+11+6+9+8 = 50.
So the experimental probability of rolling a three is 11/50 = 0.22
