Answer
The length of the side CA is \[5\].
Work Step by Step
\[\Delta ABC\] and \[\Delta ADE\]are similar where, BA \[=\] 3, CB \[=\] 3 in\[\Delta ABC\] and ED \[=\] 9, EA \[=\] 15 in \[\Delta ADE\].
Thus, \[\frac{ED}{CB}=\frac{EA}{CA}\]
Compute the value of side CA as shown below:
\[\begin{align}
& \frac{9}{3}=\frac{15}{CA} \\
& 9\times CA=15\times 3 \\
& 9CA=45 \\
& CA=5
\end{align}\]
Hence, the length of the side CA is \[5\].