Find the probability that a roll of two dice will produce a sum of 2, 3, or 12.

You can produce a sum of two if you roll: (1) and (1)

So that is a 1/36 possibility

You can produce a sum of three if you roll: (1) and (2), (2) and (1)

So that is a 2/36 possibility

You can produce a sum of twelve if you roll: (6) and (6)

So that is a 1/36 possibility

Add all of the possibilities and you get 4/36 = 1/9