Answer
See below.
Work Step by Step
The odds for $E$: $\frac{P(E)}{P(\text{not E})}$. The probability for $E$: $\frac{P(E)}{P(\text{not E})+P(E)}$. The odds against $E$: $\frac{P(\text{not E})}{P(E)}$ The probability against $E$: $\frac{P(\text{not E})}{P(\text{not E})+P(E)}$.
a) odds for $E$: $\frac{1}{P(\text{not E})}=4$
b) $P(E)=\frac{4}{4+1}=\frac{4}{5}$
