A jar contains four blue marbles and three white marbles. Three marbles are selected at random without replacement. What is the probability that all three marbles selected will be blue?

Multiply the individual probabilities ; P(1st. One blue)*P(2nd. One blue if the 1st. One was blue)*P(3rd. One blue if the 1st. Two were blue)

\frac{C(4,3)}{C(7,3)}