Answer: 6
Explanation:
In order to solve this problem it is asking you to graph each of the coordinates that you have. For example, the first one is x=3 and y=8, so you mark 3,8.
Do this for each of the four sets. What the question is asking you to do is find what the y coordinate will be for 5. After you mark each of the other 4 and connect them with a line you will see that the line goes through 5,6.
You can also look at the pattern of the numbers. As x goes up by one (3,4,5...) y is going down by one (8,7,6...). The number that you are missing is 6.