Set cong cong x Ben Ming 100-x Ben

4x/9+2( 100-x)/7 = 100-60

x=72

Cong Cong has 72 books and 28 books.

If so, the landlord is a pupil. . . Study hard and be too lazy to ask Baidu.

If you can't draw a line segment, you can solve it by drawing it in proportion.