Question 1025984
<pre>
The first solution above is correct.  
But it's not easy to see why half have 5 or more
and the other half don't.

The second solution above is incorrect.
She went for the subsets with fewer than 5 elements,
because their complements all have 5 elements or more.
That way would have been correct.  But she made a
mistake and included the subsets with 5 elements, but 
she shouldn't have because their complements have only 
4 elements. 

The correct and the easiest way to understand
is to add the combinations of 9 elements taken
5 or more.

9C5+9C6+9C7+9C8+9C9 = 126+84+36+9+1=256.

Edwin</pre>