Mary can choose 2 books out of a selection of 9 books to read for her English class. How many different possibilities would there be in choosing the committee?

No data on the committee.

To calculate the number of different possibilities in choosing the committee, we can use the concept of combinations.

In this scenario, Mary needs to choose 2 books out of a selection of 9 books. The order in which the books are selected does not matter; what matters is which books are included in the selection.

The formula to calculate combinations is:
C(n, r) = n! / (r! * (n - r)!)

Where:
C(n, r) represents the number of combinations of choosing "r" items from a set of "n" items,
n! represents the factorial of "n", which is the product of all positive integers from 1 to n.

In this case, Mary needs to choose 2 books out of 9. So, substituting into the formula:
C(9, 2) = 9! / (2! * (9 - 2)!)
= 9! / (2! * 7!)

Calculating the factorials:
9! = 9 * 8 * 7! = 9 * 8 * 7
2! = 2 * 1 = 2
7! = 7 * 6 * 5 * 4 * 3 * 2 * 1 = 7!

Substituting the factorials back into the formula:
C(9, 2) = (9 * 8 * 7) / (2 * 7!)
= (9 * 8) / 2

Simplifying the expression gives us:
C(9, 2) = 36

Therefore, there are 36 different possibilities in choosing the committee.