$\text{a)}\frac{\frac{2}{3}+1\frac{4}{5}}{0,1}=\frac{\frac{20}{30}+1\frac{24}{30}}{\frac{1}{10}}=\frac{1\frac{44}{30}}{\frac{1}{10}}=\frac{2\frac{14}{30}}{\frac{1}{10}}=\frac{74}{3\sout{0}}\cdot 1\sout{0}=\frac{74}{3}=24\frac{2}{3}$   

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$\text{b)}\frac{-1\frac{4}{5}+\frac{1}{3}}{0,2}=\frac{-1\frac{12}{15}+\frac{5}{15}}{\frac{2}{10}}=\frac{-1\frac{7}{15}}{\frac{1}{5}}=-\frac{22}{{\sout{15}}_3}\cdot {\sout{5}}^1=-\frac{22}{3}=-7\frac{1}{3}$  

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$\text{c)}\frac{0,4}{9,8+\left(-7\frac{4}{5}\right)}=\frac{0,4}{9,8-7\frac{8}{10}}=\frac{0,4}{9,8-78}=\frac{0,4}{2}=0,2$  

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$\text{d)}\frac{0,5}{-3\frac{5}{6}-1,75}=\frac{\frac{1}{2}}{-3\frac{5}{6}-1\frac{3}{4}}=\frac{\frac{1}{2}}{-3\frac{20}{24}-1\frac{18}{24}}=\frac{\frac{1}{2}}{-4\frac{38}{24}}=\frac{\frac{1}{2}}{-5\frac{14}{24}}=\frac{\frac{1}{2}}{-\frac{134}{24}}=$     

$=\left(\frac{1}{{\sout{2}}^1}\right)\cdot \left(-\frac{{\sout{24}}^{12}}{134}\right)=-\frac{12}{134}=-\frac{6}{67}$