Explanation

(b)
Given lines are
$3x + 4y = 9$ …(i)
and $6x + 8y = 15$
$\Rightarrow 3x + 4y = \frac{15}{2}$ …(ii)
∵ Both lines are parallel, therefore the distance between two
$lines = \frac{\left| \frac{15}{2} - 9 \right|}{\sqrt{3^{2} + 4^{2}}} = \frac{3}{2 \bullet 5} = \frac{3}{10}$