The probability that at least one of the events A and B happens is $\frac{3}{5}$. Probability of their simultaneous happening is $\frac{1}{5}$. Value of $P(\bar{A})+P(\bar{B})$ is equal to

$\frac{6}{5}$

$P(A \cup B)=\frac{3}{5}, P(A \cap B)=\frac{1}{5}$

Now, $P(A \cup B)=P(A)+P(B)-P(A \cap B)$

$=2-P(A \cap B)-P(\bar{A})-P(\bar{B})$

$\Rightarrow P(\bar{A})+P(\bar{B})=2-P(A \cap B)-P(A \cup B)$

$=2-\frac{1}{5}-\frac{3}{5}=\frac{6}{5}$