Thomas has a box with four black color bottles and eight gray color bottles. two bottles are drawn without replacement from the box. what is the probability that both of the bottles are gray

So 4 black and 8 grey. 4+8=12

12 Total bottles

if he takes 2 bottles out of the box, there is a 2/8 chance that he will get both grey ones, because when you have 8 total grey bottles, and you're pulling 2 out, then you have 2 in 8 chance of getting a grey bottle.