The total space of events is the space of all pairs (a,b), where "a" and "b" are integer numbers from 1 to 6 inclusively. So, the total space of events has 6*6 = 36 elements, that are such pairs (outcomes). The favorable set is the set of pairs (a,b) with a + b = 3. It consists of pairs (1,2) and (2,1), counting exactly 2 (two) elements. Therefore, the probability under the question is the ratio= . ANSWER