This premise tells us that there is at least one school that is also a college. To express this in the diagram, we need to place an x in those areas where schools and colleges overlap. 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.