\[\boxed{\mathbf{723\ (723).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[y_{17} = 22;\ \ d = 0,5\]
\[y_{17} = y_{1} + 16d \Longrightarrow\]
\[\Longrightarrow \text{\ \ }y_{1} = y_{17} - 16d\]
\[y_{1} = 22 - 16 \cdot 0,5 =\]
\[= 22 - 8 = 14.\]