\[a_{1} = 10;\ \ a_{2} = 6:\]
\[d = 6 - 10 = - 4;\]
\[a_{16} = a_{1} + 15d = 10 - 60 = - 50;\]
\[S_{30} = \frac{2a_{1} + 29d}{2} \cdot 30 =\]
\[= \left( 2a_{1} + 29d \right) \cdot 15 = (20 - 116) \cdot 15 =\]
\[= - 96 \cdot 15 = - 1440.\]
\[Ответ:a_{16} = - 50;\ \ \ S_{30} = - 1440.\]