\[\boxed{\mathbf{254}\mathbf{.}}\]
\[P_{\text{ABCD}} = 42\ см;\]
\[P_{\text{ABCDE}} = 64\ см;\]
\[AD = 14\ см;\]
\[P_{\text{AED}} - ?\]
\[P_{\text{ABCDE}} = P_{\text{ABCD}} + P_{\text{AED}} - 2AD\]
\[64 = 42 + P_{\text{AED}} - 2 \cdot 14\]
\[42 - 28 + P_{\text{AED}} = 64\]
\[14 + P_{\text{AED}} = 64\]
\[P_{\text{AED}} = 64 - 14 = 50\ (см).\]
\[Ответ:50\ см.\]