The probability of an event A occuring is 0.5 and of B occuring is 0.3. If A and B are mutually exclusive events then the probability of neither A nor B occuring is

$P\left(A\right)=0.5,P\left(B\right)=0.3,A\cap B=\varphi$

$P(A\cup B)=P\left(A\right)+P\left(B\right)$

                     $=0.5+0.3=0.8$

$P(\overline{A}\cap \overline{B})=1-0.8=0.2$

$\therefore$ The probability of neither A nor B occurring is 0.2