Question

If $P\left(E\right)=0.05$, what is the probability of 'not $E$'?

Answer 1

Sum of the probabilities of complementary events is equal to $1$, i.e.,

$P\left(E\right)+P\left(\text{not}E\right)=1$
$0.05+P\left(\text{not}E\right)=1$
$P\left(\text{not}E\right)=1-0.05$
$\therefore P\left(\text{not}E\right)=0.95$