If it helps, imagine you have 5 of something (plants, cookies, books, whatever helps) and 7 of the same thing. If you picture them together, you'll have 12.
With 2 dices we have all 6x6=36 ways. But for two conditions: sum 8 and both even numbers, we have only: (2;6), (6;2), (4;4). That's all. And the probability is 3/36= 1/12 Have fun
