\[\boxed{\mathbf{213.}}\]
\[\textbf{а)}\ 1 - \frac{1}{4} = \frac{3}{4};\]
\[\textbf{б)}\ 1 - 0,02 = 0,98;\]
\[\textbf{в)}\ 1 - \frac{2}{7} = \frac{5}{7};\]
\[\textbf{г)}\ 1 - 0,83 = 0,17.\]