Solution

Let 

$R_M$ and $R_W$ be the event that a man and woman, respectively, remains in particular company for 10 years or more.

Given: $P(R_M)=P(R_W)= \dfrac{1}{6}$

a.

$$\begin{align*} P(R_M^c)&= 1 - P(R_M)\\ &= 1- \dfrac{1}{6}\\ &= \dfrac{5}{6} \end{align*}$$

Answer

a. $\dfrac{5}{6}$  b. $\dfrac{25}{36}$ c.  $$\dfrac{11}{36}