An experiment consists of rolling two fair number cubes. What is the probability that the sum of the two numbers will be 8? Express your answer as a fraction in simplest form.

ⓐ- 5/36
ⓑ- 1/9
ⓒ- 36/5
ⓓ- 31/36



I know that the answer is A, they give us the answer but we need to provide work and I don't understand how we get the answer.