Distance  between two parallel planes $2x + y + 2z = 8$ and $ 4x + 2y + 4z + 5 = 0, $ is

$\frac{3}{2}$ $\frac{5}{2}$ $\frac{7}{2}$ $\frac{9}{2}$

$\frac{7}{2}$

Equations of the given  planes are $2x + y + 2z- 8 = 0 $ and $2x + y + 2z +\frac{5}{2}= 0 $. Let d be the distance between these planes. Then, $d = \begin{vmatrix} \frac{-8-\frac{5}{2}}{\sqrt{2^2 + 1^2 + 2^2}}\end{vmatrix}= \frac{21}{6}=\frac{7}{2}$