\[\sqrt{3 + \sqrt{5 + \sqrt{x}}} = 3\ \ \]
\[3 + \sqrt{5 + \sqrt{x}} = 9\]
\[\sqrt{5 + \sqrt{x}} = 6\]
\[5 + \sqrt{x} = 36\]
\[\sqrt{x} = 31\]
\[x = 961.\]