The only such area that has not been shaded, however, is the area where the three rectangles overlap. So we know that something exists in this area. We must, therefore, place a capital X in this area. All schools are educational institutions. Some schools are colleges.
Some colleges are educational institutions.
All that remains to be done is to find out whether the conclusion of the argument follows from its premises. If it does, then the argument is valid. Otherwise, it is invalid. Clearly, the argument in question is valid. Let's try one more example.