Ответ:
\[a_{12} + a_{36} = 400\]
\[a_{1} + 11d + a_{1} + 35d = 400\]
\[2a_{1} + 46d = 400\]
\[a_{1} + 23d = 200\]
\[a_{24} = 200\]
\[Ответ:200.\]
\[a_{12} + a_{36} = 400\]
\[a_{1} + 11d + a_{1} + 35d = 400\]
\[2a_{1} + 46d = 400\]
\[a_{1} + 23d = 200\]
\[a_{24} = 200\]
\[Ответ:200.\]