\[\boxed{\text{6.224.}}\]
\[\textbf{а)}\ \frac{1}{4} = \frac{25}{100} = 0,25;\ \]
\[\textbf{б)}\ \frac{7}{8} = 0,875;\ \]
\[\textbf{в)}\ \frac{9}{4} = 2\frac{1}{4} = 2\frac{25}{100} = 2,25;\]
\[\textbf{г)}\ \frac{93}{15} = \frac{31}{5} = \frac{62}{10} = 6,2;\ \]
\[\textbf{д)}\ 2\frac{3}{5} = 2\frac{6}{10} = 2,6;\]
\[\textbf{е)}\ 80\frac{6}{75} = 8\frac{2}{25} = 8\frac{8}{100} =\]
\[= 80,08;\ \]
\[\textbf{ж)}\ 7\frac{13}{52} = 7\frac{1}{4} = 7\frac{25}{100} = 7,25.\]