Answer:
The answer is 13.
Step-by-step explanation: In order to find the average in a set of numbers, you must add all numbers and divide them by the numbers of numbers which you have added.
For example for your problem, I added 12 + 4 +16 +20 and I got 52. Then count the numbers which u have added. There are 4 numbers I have added. Then divide that number by the total. So it would be 52/4 and once you divide, you have your answer!
Hope this helps!