Each cube can land in any one of 6 ways.
Two cubes can land in any one of (6 x 6) = 36 ways.
The "successful" outcomes are those for which the sum is 4 .
How many ways can that happen ?
1 . . . 3
3 . . . 1
2 . . . 2
It can happen in 3 ways out of the 36 possible outcomes.
So the probability is
3 / 36 = 1 / 12 .
In a large number of rolls, you expect success roughly
once out of every 12 rolls.
In 10,000 rolls, you expect success (10,000 / 12) = about 833 times.
