Solution :

Let A be the event that husband is selected and B be the event that the wife is selected

then $P(A) =\large\frac{1}{7}$ and $P(B) =\large\frac{1}{5}$

$P(\bar {A}) =\bigg(1- \large\frac{1}{7} \bigg) =\large\frac{6}{7}$

$P(\bar {B}) =\bigg(1- \large\frac{1}{5} \bigg) =\large\frac{4}{5}$

Required probability is

$P(A) .P(\bar {B}) +P( \bar {A}) . P(B) $

$\qquad = \large\frac{1}{7} \times \large\frac{4}{5} +\large\frac{1}{5} \times \large\frac{6}{7}$

$\qquad= \large\frac{2}{7}$