This is a concept of combination, the question requires us to find out how many combinations of students a teacher can choose if she sends 3 of her student to pick up books for the class. Since there is no specific order in selection, the combination will be given by:
nCr
n=Total number of the sample
r=number of students o be selected
thus the combination will be:
18C3
=816
This implies that there are 816 ways in which the Ms Washington can select the students
