Kyra observed that 85% of the students at a library liked reading mystery stories. if 30 students at the library did not like reading mystery stories, the number of students at the library who liked mystery stories was (only put numeric values, no other symbols)

The first thing we must do is find the percentage of students who do not like to read mystery stories.
 We have then:
 
 Then, to find the number of students who like to read mystery stories, we can make the following rule of three:
 15% ----------------> 30 students
 85% ----------------> x
 From here, we clear the value of x.
 We have then:
 
 
 the number of students at the library who liked mystery stories was 170