\[a_{1} + a_{2} + a_{3} = 111:\]
\[a_{1} + a_{1} + d + a_{1} + 2d = 111\]
\[3a_{1} + 3d = 111\]
\[a_{1} + d = 111\ :3\]
\[a_{1} + d = 37 \Longrightarrow a_{2} = 37.\]
\[a_{2} = 5a_{1}\]
\[5a_{1} = 37\]
\[a_{1} = 7,4.\]
\[Ответ:7,4.\]