Answer
$\frac{1}{2}$
Work Step by Step
P(E) = $\frac{no.\ of\ outcomes\ in\ favor}{Total\ no\ of\ outcomes}$
S={1,2,3,4,5,6}, so there are 6 total outcomes.
There are 3 favorable outcomes (rolling a 4,5,6).
P(E) = $\frac{3}{6}$ = $\frac{1}{2}$