Step-by-step explanation:
we are given 2 red balls, 3 green balls and 4 blue balls for a total of 9 balls in the hat. we are to take two balls and find the probability that both are blue.
the first probability would be

as probability is equal to (number of favorable outcomes) / number of total outcomes). so we have 9 total outcomes and 4 favorable ones (4 balls we want)
next, we have remaining 2 red balls, 3 green balls, 3 blue balls and 8 total balls. again, the second probability is

we have 8 total outcomes and 3 favorable ones (3 blue balls we want).
thus, their product is our total probability.

thus, our probability is 1/6.