\[\boxed{\mathbf{3.}\mathbf{101}}\]
\[\textbf{а)}\ x\ :7 - 2 = 4\]
\[x\ :7 = 4 + 2\]
\[x = 6 \cdot 7\]
\[x = 42\]
\[Ответ:число\ 42.\]
\[\textbf{б)}\ (x - 36) \cdot 5 = 240\]
\[x - 36 = 240\ :5\]
\[x = 48 + 36\]
\[x = 84\]
\[Ответ:число\ 84.\]