Answer
$\displaystyle \frac{7}{10}$
Work Step by Step
The empirical probability of event $E$ is
$P(E)=\displaystyle \frac{observed\ number\ of\ times\ E\ occurs}{total\ number\ of\ observed\ occurrences}$
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The total number of movie goers is :
900+1080+840+180=3000
The observed number of E, a movie goer being between 19 and 24, is:
$P(E)=\displaystyle \frac{900}{3000} =\displaystyle \frac{3}{10}$
The probability of this event not occurring, therefore, is:
$P($not E$)=1-\displaystyle \frac{3}{10}=\frac{7}{10}$