Test and analysis: (1) According to the fact that the absolute values of positive numbers and 0 are themselves and the absolute values of negative numbers are their antonyms, it can be simplified;

(2) There are X students. According to 3 books per student, the remaining 20 books, 4 books per student, and 25 books missing, the equation can be solved.

( 1)│- x │+│x+4 │-│x-4；

(2) There are X students, which are derived from the meaning of the question.

solve

A: There are 155 books and 45 students.

Comments: The key to solving a problem is to read the meaning of the problem, find the equivalence relationship, list the equations correctly, and then solve them.