$\text{a)}6,075:\frac{3}{2}-\frac{5}{7}\left(\frac{1}{5}+2,6\right)=6\frac{75}{1000}\cdot \frac{2}{3}-\frac{5}{7}\left(\frac{1}{5}+\frac{26}{10}\right)=$  

$=6\frac{3}{40}\cdot \frac{2}{3}-\frac{5}{7}\left(\frac{1}{5}+\frac{13}{5}\right)=\frac{{\sout{243}}^{81}}{{\sout{40}}_{20}}\cdot \frac{{\sout{2}}^1}{{\sout{3}}_1}-\frac{{\sout{5}}^1}{{\sout{7}}_1}\cdot \frac{{\sout{14}}^2}{{\sout{5}}_1}=\frac{81}{20}-2=$  

$=4\frac{1}{20}-2=2\frac{1}{20}$  

---

$\text{b)}\frac{\left(1,6:\frac{11}{7}+0,5:1\frac{1}{4}-\frac{2}{11}\right)\cdot 3}{\left(2\frac{1}{5}-0,2\right)\cdot \frac{17}{11}}=\frac{\left(\frac{16}{10}\cdot \frac{7}{11}+\frac{1}{2}:\frac{5}{4}-\frac{2}{11}\right)\cdot 3}{\left(\frac{11}{5}-\frac{1}{5}\right)\cdot \frac{17}{11}}=$  

$=\frac{\left(\frac{8}{5}\cdot \frac{7}{11}+\frac{1}{{\sout{2}}_1}\cdot \frac{{\sout{4}}^2}{5}-\frac{2}{11}\right)\cdot 3}{\frac{10}{5}\cdot \frac{17}{11}}=\frac{\left(\frac{56}{55}+\frac{2}{5}-\frac{2}{11}\right)\cdot 3}{2\cdot \frac{17}{11}}=\frac{\left(\frac{56}{55}+\frac{22}{55}-\frac{10}{55}\right)\cdot 3}{\frac{34}{11}}=$  

$=\frac{\left(\frac{78}{55}-\frac{10}{55}\right)\cdot 3}{\frac{34}{11}}=\frac{\frac{68}{55}\cdot 3}{\frac{34}{11}}=\frac{\frac{204}{55}}{\frac{34}{11}}=\frac{{\sout{204}}^6}{{\sout{55}}_5}\cdot \frac{{\sout{11}}^1}{{\sout{34}}_1}=\frac{6}{5}=1\frac{1}{5}$  

---

$\text{c)}\left(\frac{3\frac{1}{4}-1\frac{1}{3}}{1\frac{3}{8}+1\frac{1}{2}}-\frac{2,75-\frac{3}{2}}{0,125+0,5}\right)\cdot \frac{3}{4}=\left(\frac{\frac{13}{4}-\frac{4}{3}}{\frac{11}{8}+\frac{3}{2}}-\frac{2\frac{3}{4}-\frac{3}{2}}{\frac{1}{8}+\frac{1}{2}}\right)\cdot \frac{3}{4}=$  

$=\left(\frac{\frac{39}{12}-\frac{16}{12}}{\frac{11}{8}+\frac{12}{8}}-\frac{\frac{11}{4}-\frac{6}{4}}{\frac{1}{8}+\frac{4}{8}}\right)\cdot \frac{3}{4}=\left(\frac{\frac{23}{12}}{\frac{23}{8}}-\frac{\frac{5}{4}}{\frac{5}{8}}\right)\cdot \frac{3}{4}=$  

$=\left(\frac{{\sout{23}}^1}{{\sout{12}}_3}\cdot \frac{{\sout{8}}^2}{{\sout{23}}_1}-\frac{{\sout{5}}^1}{{\sout{4}}_1}\cdot \frac{{\sout{8}}^2}{{\sout{5}}_1}\right)\cdot \frac{3}{4}=\left(\frac{2}{3}-2\right)\cdot \frac{3}{4}=\left(\frac{2}{3}-\frac{6}{3}\right)\cdot \frac{3}{4}=$  

$=\left(-\frac{4}{3}\right)\cdot \frac{3}{4}=-1$