To determine the median, let's put the numbers from least to greatest WITHOUT x.
3, 6, 8, 12, 13, 13, 13, 15.
Let's look at our current median.
12.5 is our current median.
Now let's insert 1.
1, 3, 6, 8, 12, 13, 13, 13, 15.
3, 6, 8, 12, 13, 13, 13.
6, 8, 12, 13, 13.
8, 12, 13.
12.
If we were to insert 1, our median would be 12.
Now let's insert 20.
3, 6, 8, 12, 13, 13, 13, 15, 20.
6, 8, 12, 13, 13, 13, 15.
8, 12 ,13, 13, 13.
12, 13, 13.
13.
If we were to insert 20, our median would be 13.
Your answer is 1.
I hope this helps!