Question

Two fair 6-sided dice are rolled. What is the probability the sum rolled is 9?

Answer 1

Each dice has six combinations which are independent. Therefore the number of possible outcomes will be 6*6 = 36. The probability of rolling a pair of dice whose numbers add to 5 is 4/36 = 1/9.

Answer 2

The probability is

        (number of ways to roll a 9) / (total possible different rolls) .

Each cube can land in 6 different ways, so the total possible rolls = 36 .

How many different rolls can be a sum of 9 ?
I don't know.  Let's countum:

Cube-A  Cube-B
     3            6
     4            5
     5            4
     6            3

Did I miss any ?  I don't think so.  There are four (4) ways to roll a 9.

So the probability is      4 / 36  =  1/9  =  11.1%