Seventy-five percent or 15 of the students in emily's homeroom class are going on the field trip two thirds or 12 of the students in santiago's homeroom class are going on the field trip. which class has more students? justify your answer

Let x be the number of students in Emily's class such that 75% of x is 15. 
                                        15 = 0.75x
The value of x is equal to 20.  
Let y be the number of students in Santiago's class. Similar with what we did previously,
                                          12 = (2/3)y
The value of y is equal to 18. 
Therefore, there are more student's in Emily's class than in Santiago's class.