There are 9 students in a class. the teacher chooses 2 students to go to the
library. the order in which they are chosen does not matter. how many ways
are there to choose the students?

72

Step-by-step explanation:

There are 9 students to choose from to go the library. After that person is chosen there are 8 students remaining.

First student  and   Second student

           9           x               8                 = 72

c

Step-by-step explanation:

You just add the two equations together and add like terms and that's what your final equation is.