\[\boxed{\text{4.\ 359}}\]
\[\textbf{а)} - 3,78\ :4,2 + 49,49\ :4,9 =\]
\[= - 0,9 + 10,1 = 9,2\]
\[\textbf{б)}\ 1,35\ :( - 1,5) + 98,98\ :9,8 =\]
\[= - 0,9 + 10,1 = 9,2\]
\[\textbf{в)}\ (1 - 1,2 \cdot 1,7) \cdot ( - 3,5) =\]
\[= (1 - 2,04) \cdot ( - 3,5) =\]
\[= 1,04 \cdot 3,5 = 3,64\]
\[\textbf{г)}\ (1 - 1,4 \cdot 1,8) \cdot ( - 1,5) =\]
\[= (1 - 2,52) \cdot ( - 1,5) =\]
\[= 1,52 \cdot 1,5 = 2,28\]
\[\textbf{д)}\ \left( \frac{2}{3} - \frac{7}{9} \right)\ :1\frac{2}{9} = \left( \frac{6}{9} - \frac{7}{9} \right)\ :\frac{11}{9} =\]
\[= - \frac{1}{9} \cdot \frac{9}{11} = - \frac{1}{11}\]
\[\textbf{е)}\ \left( - \frac{3}{4} + \frac{15}{16} \right)\ :\left( - 1\frac{1}{8} \right) =\]
\[= \left( - \frac{12}{16} + \frac{15}{16} \right)\ :\left( - \frac{9}{8} \right) =\]
\[= \frac{3}{16} \cdot \left( - \frac{8}{9} \right) = - \frac{1}{6}\]