You will have to add all of the numbers up and then divide by how many numbers you see
5+ 1+ 15+ 43+ 9+ 9+ 11+ 11+ 14+ 12+ 36+ 6= 172
Now we will count how many number there are.
there are 12 numbers.
Now we divided 172 and 12 to get the Mean(Average)
We get 14.3333333 as our Mean if we simplify you get 14.3