Probability is found by putting the number of ways things can happen over the total possible outcomes.
The number of ways we could add to 4 with two dice is 1+3, 2+2, or 3+1. That's 3 ways.
Then we count every pairing of dice in the image. That adds to 36.
So the probability of rolling to add to 4 is 3/36 or 1/12.
