Since we want the median to be 8, this means that there needs to be enough of x so that the mid-point will be exactly on the last 8. Counting from the back, there are 11 numbers to the right of the last 8, so there should also be 11 numbers to the left of the last 8.

To visualise:

6, 6, 6, 6, 6, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11

This means that there should be three sevens. So minimum value of x = 3.

thks so much Adwin