\[\boxed{\text{6.103.}}\]
\[\textbf{а)}\ 0,4 < x < 0,5\ \ \ \]
\[x = 0,43;\ \ 0,47.\ \]
\[\textbf{б)}\ 0,06 < x < 0,07\ \ \]
\[x = 0,0601;\ \ 0,068.\ \]
\[\textbf{в)}\ 0 < x < 0,0001\ \ \ \]
\[x = 0,000001;\ \ 0,00001.\ \ \ \]