Answer
P(blue then blue)= $\frac{1}{35}$
Work Step by Step
The marbles are not replaced, so the events are dependent:
3 of the 15 marbles are blue:
P(blue)=$\frac{3}{15}$=$\frac{1}{5}$
2 of the 14 remaining marbles are blue:
P(blue after blue)=$\frac{2}{14}$=$\frac{1}{7}$
P(blue then blue)=P(blue) $\times$ P(blue after blue)
P(blue then blue)=$\frac{1}{5}$ $\times$ $\frac{1}{7}$= $\frac{1}{35}$
P(blue then blue)= $\frac{1}{35}$
