You draw two identical line segments, one divided into four small segments and the other into five small segments; Take 25% from the first article, that is, 1/4, and then take 3/5 from the second article, so that you can know how much the first article is longer than the rest of the second article (fractional value); Then, according to the title, take 15 books from the upper level and put them in the lower level, indicating that the upper level is more than the lower level (15+15)/[(1-25%)-(1-2/5)] = 200.