Answer: There are 4 students in the group.
Step-by-step explanation:
Let the number of students in the group be n
If one of them scored 9 more points , their average score would be 81 points.
So, our equation (1) will be
Similarly,
If one of them scored 3 points less, their average score would be 78 points.
So, our equation (2) will be
So, from equation (1) and (2) we get:
Hence, there are 4 students in the group.