\[\boxed{\text{205\ (205).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[1)\ a^{5} \cdot a^{8} = a^{5 + 8} = a^{13}\]
\[2)\ a^{2} \cdot a^{2} = a^{2 + 2} = a^{4}\]
\[3)\ a^{9} \cdot a = a^{9 + 1} = a^{10}\]
\[4)\ a \cdot a^{2} \cdot a^{3} = a^{1 + 2 + 3} = a^{6}\]
\[5)\ (m + n)^{13} \cdot (m + n) =\]
\[= (m + n)^{13 + 1} = (m + n)^{14}\]
\[6)\ \left( \text{cd} \right)^{8} \cdot \left( \text{cd} \right)^{18} \cdot cd =\]
\[= (c{d)}^{8 + 18 + 1} = \left( \text{cd} \right)^{27}\]