\[\boxed{\mathbf{400}\mathbf{.}}\]
\[1)\ \frac{11}{18} - \frac{14}{27}x = \frac{5}{12}\]
\[\frac{14}{27}x = \frac{11^{\backslash 2}}{18} - \frac{5^{\backslash 3}}{12}\]
\[\frac{14}{27}x = \frac{22}{36} - \frac{15}{36}\]
\[\frac{14}{27}x = \frac{7}{36}\]
\[x = \frac{7}{36}\ :\frac{14}{27}\]
\[x = \frac{7}{36} \cdot \frac{27}{14}\]
\[x = \frac{1 \cdot 3}{4 \cdot 2}\]
\[x = \frac{3}{8}.\]
\[2)\ \frac{1^{\backslash 20}}{3}x + \frac{1^{\backslash 15}}{4}x + \frac{1^{\backslash 12}}{5}x =\]
\[= 1\frac{19}{75}\]
\[\frac{20 + 15 + 12}{60}x = 1\frac{19}{75}\]
\[\frac{47}{60}x = \frac{94}{75}\]
\[x = \frac{94}{75}\ :\frac{47}{60}\]
\[x = \frac{94}{75} \cdot \frac{60}{47}\]
\[x = \frac{2 \cdot 4}{5 \cdot 1} = \frac{8}{5}\]
\[x = 1\frac{3}{5}.\]