“What are the chances of picking a non-green one in the first pick”
75%
“a white one on the second pick?”
25% (75% chance you didn’t pick white on the first pick * 33.3% chance you pick white on the second pick.)
The probability of picking a non-green one in the first pick AND picking a white one on the second pick is .1875 or 3/16 (.75 * .25).