Each question has 3 possible answers. If guessing at random, there is a one in 3 chance, i.e. 33.3% or 1/3 chance, of getting a particular question right. This is the same probability for each of the 12 questions.
Therefore, if there is a 33.3% or 1/3 chance of getting any given question right, and there are 12 questions, then the total number of questions Jason will expect to get right is 1/3*12 = 4.
