Answer:
Afternoon class has more students.
Step-by-step explanation:
Let m be the number of students in the morning class and n be the number of students in the afternoon class.
The average score for the students in the morning class was 80, then the sum of their scores is 
The average score for the students in the afternoon class was 86, then the sum of their scores is 
The sum of the scores of both classes is

and the average score is

The average (arithmetic mean) score for the two classes combined was 84, then

This means n is greater, so afternoon class has more students.