\[3,85 \cdot (d - 4,02) = 8,47\]
\[d - 4,02 = 8,47\ :3,85\]
\[d - 4,02 = 2,2\]
\[d = 2,2 + 4,02\]
\[d = 6,22.\]
\[Ответ:\ d = 6,22.\]