An experiment consists of rolling two fair (not weighted) dice and adding the dots on the two sides facing up. Each die has the number 1 on two opposite faces, the number 2 on two opposite faces, and the number 3 on two opposite faces.

Compute the probability of obtaining the indicated sums in problem.

Just regular dice, it has total possible outcomes. You will see there are 12 of them have a total of 4, if you would see.

So, the answer would be

12/36 = 1/3

the rest can also be obtained by counting. the probability you get a sum of 2 is

4/36

So, for a sum of 6 and the probability you get a sum of 3 and the probability you get a sum of 5 is 8/36