The answer is 5.25
First, you need to list all of the numbers from least to greatest. Then, you remove the sides (first 3.9 and 6.2 being the least and the greatest numbers). You then have 4.9 and 5.6 so you need to add them together (getting 10.6) and divide your answer by 2 (getting 5.25).
Hope I helped and good luck :)