\[\boxed{\mathbf{750}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
\[\textbf{а)}\]
\[= 82\ см.\]
\(S = S_{1} + S_{2}\)
\[S_{1} = 5 \cdot 8 = 40\ см^{2}.\]
\[S_{2} = 18 \cdot 15 = 270\ см^{2}.\]
\[S = 40 + 270 = 310\ см^{2}.\]
\[Ответ:82\ см;\ \ 310\ см^{2}.\]
\[\textbf{б)}\]
\(S = S_{1} + S_{2}\)
\[S_{1} = 11 \cdot 18 = 198\ см^{2}.\]
\[S_{2} = 6 \cdot 3 = 18\ см^{2}.\]
\[S = 198 + 18 = 216\ см^{2}.\]
\[Ответ:\ \ 70\ см;\ 216\ см^{2}.\]