Explanation:
3 white + 2 green + 2 red + 1 blue = 8 total
We're told the first marble is white, so there are now 8-1 = 7 total
The probability of picking red on the second selection, based on the given info, is 2/7 since we have 2 red marbles out of 7 total leftover. The answer would be 2/8 = 1/4 if we didn't know what the color of the first marble was.
