Solution

Let 

$R_M$ and $R_W$ be the event that a man and his wife, respectively, waits at counter for more than 5 minutes.

Given: $P(R_M)=P(R_W)= 0.2$

a.

$$\begin{align*} P(R_M^c)&= 1 - P(R_M)\\ &= 1- 0.2\\ &= 0.8 \end{align*}$$

Answer

a. $0.8$ b. $0.64$ c. $0.36$

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