\[\boxed{\text{5.179.}}\]
\[\textbf{а)}\ \frac{18}{29} - \frac{6}{29} = \frac{12}{29}\ \]
\[\textbf{б)}\ \frac{18}{29} - \frac{12}{29} = \frac{6}{29}\ \]
\[\textbf{в)}\ x + \frac{12}{29} = \frac{18}{29}\]
\[x = \frac{6}{29}\text{.\ }\]
\[\textbf{г)}\ \frac{6}{29} + y = \frac{18}{29}\]
\[y = \frac{12}{29}\text{.\ \ }\]