Regardless, begin by arranging the data in order:

3, 4, 5, 6, 6, 7, 8, 9, 9, 11

Now, there are ten sample data points. We are looking for one value that essentially is less than roughly 75% of the remaining data.

So, 25% of 10 = 2.5; rounded up to 3 since 5 has two numbers less than it (20% of the data, which is obviously less than 25%.)

I am sure the question is a little more specific, because, technically, the way that you word it leaves 3 and 4 as valid answers too. (Choosing 3, 0% is certainly less than 25%.)