## Precalculus (10th Edition)

a) $\frac{25}{33}$ b) $\frac{25}{33}$
We know that probability$=\frac{\text{number of favourable outcomes}}{\text{number of all outcomes}}.$ a) In total there are $18+15=33$ students, out of which $18$ are freshmen (including females) and $15-8=7$ are sophomore females. Thus the probability=$\frac{18+7}{33}=\frac{25}{33}$ b) In total there are $18+15=33$ students, out of which $15$ are sophomores (including males) and $10$ are freshmen males. Thus the probability=$\frac{15+10}{33}=\frac{25}{33}$