an urn contains 7 red marbles, 2 green marbles, and 5 black marbles. If a single marble is drawn from the urn, what is the probability that it is black.

The black marbles make up 35.71% of the total marbles (5 black marbles divided by 7 red, 2 green, and 5 black marbles). Thus the probability that it is black is 35.71%.