You have a case in which you have the probability of obtaining six different results: 1, 2, 3, 4, 5 and 6
The probaility of getting a specific number is given by the formula:
p = 1/n = 1/6
where n is tha number of different cases, which is 6.
To calculate the probability of getting two results, you have to multiply the probability of one result with the probaility of the other one.
The probability of getting a 4 is:
1/6
The probability of getting a 3 is:
1/6
Then, the probaility of getting the two previous results is:
P = (1/6)(1/6) = 1/36