\[\boxed{\mathbf{Вариант\ 1.}}\]
\[\boxed{\mathbf{1.}}\]
\[\boxed{\mathbf{2.}}\]
\[1)\ x\ :7 = 275 + 425\]
\[x\ :7 = 700\]
\[x = 700 \cdot 7\]
\[x = 4900.\]
\[Проверка:\]
\[4900\ :7 = 275 + 425\]
\[700 = 700.\]
\[2)\ 90\ :y = 15 \cdot 2\]
\[90\ :y = 30\]
\[y = 90\ :30\]
\[y = 3.\]
\[Проверка:\]
\[90\ :3 = 15 \cdot 2\]
\[30 = 30.\]
\[\boxed{\mathbf{3.}}\]