Answer
See below.
Work Step by Step
a) In this case the events are independent; the first one has probability $\frac{8}{16}$, and the second one has probability $\frac{8}{16}$. Thus the probability is: $\frac{8}{16}\frac{8}{16}=\frac{1}{2}$
b) In this case the events are not independent; the first one has probability $\frac{8}{16}$, and the second one has probability $\frac{7}{15}$. Thus the probability is: $\frac{8}{16}\frac{7}{15}=\frac{7}{30}$
