Answer:
Letters can be chosen in 12 different ways, if order matters, or 6 different ways, if order doesn't matter.
Explanation:
Since we want to choose 2 letters, without replacement, from the 4 letters A, B, C, and D, to determine in how many ways can this be done, if the order of the choices matters, and in how many ways can this be done, if the order of the choices does not matter, the following calculations must be performed:
If order matters =
(4 x 3 x 2 x 1) / 2 = X
24/2 = X
12 = X
If the order doesn't matter =
12/2 = X
6 = X
Therefore, letters can be chosen in 12 different ways, if order matters, or 6 different ways, if order doesn't matter.